HIGH SCHOOL 
BOTANY 



fSit vV ^ 




i£ 



BERGEN 




Class _A.Il^I 
Book Bo 



COPyRlGHT DEPOSIT. 




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"a/ 



Frontispiece. —A Shade Flant, Jack-in-the-Pulpit 



HIGH SCHOOL BOTANY 



BY 

JOSEPH y. BERGEN, A.M. 

Instkuctok in BroLOGY, EN<iLiSH High S< hoot.. Boston 



BOSTON, U.S.A. 
GINN & COMPANY, PUBLISHERS 

1904 



LIBRARY of CONGRESS 
Two GoDies Received 

APR 29 1904 

Cooyrlght Entry 
CLASS Ot, xXc. No. 



<>)rvK.]GHT, 1901, 1004 
Bv .JOSEPH Y. BEKGEN 



A 1,1. KKxHTS ItKSKKVKI) 






PEEFACE 

This book is written upon the same plan as the author's 
Elements of Botany. A few chapters stand here but little 
altered from the former work, but most of them have been 
rewritten and considerably enlarged, and many new ones 
have been added. The principal changes in the book as a 
whole are these : 

1. Most of the discussion of ecological topics is put by 
itself, in Part II. 

2. The amount of laboratory work on the anatomy and 
physiology of seed-plants is considerably increased and addi- 
tional experiments are introduced. 

3. The treatment of spore-plants is greatly extended, so as 
to include laboratory work on the most important groups. 

4. The meagre Flora which accompanied the earlier book 
has been replaced by one which contains fairly full descrip- 
tions of nearly seven hundred species of plants. Most of 
these are wild, but a considerable number of cultivated species 
have been included, mainly for the convenience of schools in 
large cities. 

Ample material is offered for a year's course, four or five 
periods per week. The author is well aware that most schools 
devote but half a year to botany, but the tendency sets strongly 
toward allowing more time for this subject. Even in schools 
where the minimum time allowance is devoted to botany, there 
is a distinct advantage in being provided with a book which 
allows the teacher considerable option as regards the kind 
and amount of work which he shall offer to his classes. 



IV PEEFACE 

Suggestions are made in the teacher's Handbook, whicli 
accompanies this volume, in regard to shaping half-year 
courses. 

The latest authorities in the various departments of botany- 
have been consulted on all doubtful points, and the attempt 
has been to make the book scientifically accurate throughout, 
yet not unduly difhcult. 

Most of the illustrations have been redrawn from those in 
standard German works of an advanced character, or drawn 
from nature or from photographs, expressly for this book. 
Besides the sources of drawings acknowledged in the author's 
Elements, many cuts have been taken from the botanies of 
Frank, Prantl, Detmer, Murray, and Bennett and Murray, as 
well as from Schimper's Pflanzengeographie. 

Of the drawings from nature or from photographs, some 
figures, and Plates I, VII, and YIII, are by Mr. Edmund 
Garrett of Boston ; several figures, the Frontispiece, and 
Plates II, IV, X, XI, are by Mr. Bruce Ilorsfall of New York ; 
several figures are by Mr. F. Schuyler Mathews of Boston ; a 
large number of figures and Plate V are by Mr. E. N. Fischer 
of Boston; several figures are by Mr. E. E. Kingsbury of Boston 
and Dr. J. W. Folsom of the University of Illinois. 

Thanks for the use of photographs are due to Mr. H. G. 
Peabody of Boston (Fig. 234), to Mr. J. H. White of Boston 
(Figs. 32, 75, 222), to Professor Conway MacMillan of the Uni- 
versity of Minnesota (Frontispiece), and to Professor F. V. 
Coville of Washington (Plate VII). Figs. 28 and 275 are 
taken by permission from the Primer of Forestry, issued by the 
Division of Forestry, U. S. Department of Agriculture. Figs. 
263, 264, 276 are copied by permission from Professor W. J. 
Beal's Seed Dispersal, and Figs. 22Q, 229, 233 from Professor 
W. M. Davis's Physical Geography. Fig. 269 is from a photo- 
graph by Professor C. F. Millspaugh of Chicago. Plate IV 
is from a photograph by Dr. H. J. Webber. 



PREFACE V 

Most of the redrawn illustrations (not microscopical) from 
various European sources are by Mr. Fischer. Most of the 
microscopical ones (and a number of figures from nature) are 
by Dr. J. W. Folsom of the University of Illinois, and many 
of both classes are by Mr. Mathews. Thanks are due to 
Professor J. M. Holzinger of the Winona (Minn.) State 
Normal School, to Professor L. Murbach of the Detroit High 
School, and to Mr. I. S. Cutter of Lincoln, Nebraska, for 
their many discriminating criticisms of the proof of Parts I 
and II. Mr. Samuel F. Tower of the Boston English High 
School, Professor Charles V. Piper of the Washington State 
Agricultural College, and Dr. Rodney H. True, Lecturer on 
Botany at Harvard University, have all read the whole or 
large portions of Part I and given valuable suggestions. 
Professor W. F. Ganong, of Smith College, has read and 
criticised Part 11. 

The chapters on spore-plants, excepting a small amount of 
matter retained from the Elements of Botany, are entirely the 
work of Mr. A. B. Seymour of the Cryptogamic Herbarium of 
Harvard University. 

The author has attempted to steer a middle course between 
the advocates of the out-of-door school and of the histological 
school of botany teaching. He has endeavored never to use a 
technical term where he could dispense with it, and on the 
other hand, not to become inexact by shunning necessary 
terms. In deciding questions of this sort, a priori reasoning 
is of little value ; one must ascertain by repeated trials how 
much of a technical vocabulary the average beginner in botany 
can profitably master. The teacher who has discovered that 
not one of the boys in a division of thirty-six pupils knows 
that his own desk-top is of cherry wood may well hesitate 
about beginning his botany teaching with a discourse on cen- 
trospheres and karyokinesis. It has been assumed throughout 
this book that, other things being equal, the knowledge is of 



VI PREFACE 

most worth which, touches the pupil's daily life at the most 
points, and therefore best enables him to understand his own 
environment. On the other hand, the author has no sympathy 
with those who decry the use of apparatus in botany teaching 
in secondary schools and who would confine the work of their 
pupils mainly within the limits of what can be seen with the 
unaided eye. If the compound microscope plainly reveals 
things shown only imperfectly by a magnifier and not seen at 
all with the naked eye, — use the microscope ! If iodine 
solution or other easily prepared reagents make evident the 
existence of structures or substances not to be detected with- 
out them, — then use the reagents ! No one thinks of deny- 
ing a boy the use of a spyglass or a compass for his tramps 
afield or his outings in a boat because he has not studied 
physics. No one would refuse to let an intelligent boy or 
girl use a camera because the would-be photographer had not 
mastered the chemical reactions that follow upon the expo- 
sure of a sensitized plate. Yet it is equally illogical to defer 
some of the most fascinating portions of botanical study until 
the college course, to which most never attain. When the 
university professor tells the teacher, that he ought not to 
employ the ordinary appliances of elementary biological inves- 
tigation in the school laboratory because the pupils cannot 
intelligently use them, the teacher is forced to reply that the 
professor himself cannot intelligently discuss a subject of 
which he has no personal knowledge. The pupils are deeply 
interested; they prove by their drawings and their recita- 
tions that they have seen a good way into plant structures 
and plant functions ; then why not let them study botany 

in earnest ? 

J. Y. B. 

Cambridge, January, 1901. 



CONTENTS 



Paet I j 

STRUCTURE, FUNCTIONS, AND CLASSIFICATION OF PLANTS 

CHAPTER I i 

PAGES i 

The Seed and its Germination 5-13 I 

CHAPTER II . 

Storage of Food in the Seed ...... 14-24 

CHAPTER III i 

Movements, Development, and Morphology of the Seedling 25-35 

CHAPTER IV ^ 

i 
Roots 36-61 

CHAPTER V I 

Stems 62-82 

CHAPTER VI i 

Structure op the Stem . . . ... . . . 83-103 ' 

CHAPTER VII 1 

Living Parts of the Stem ; Work of the Stem . . . 104-118 i 

CHAPTER VIII 

Buds 119-129 j 

vii 



Vill CONTENTS ' 

. ' I 

CHAPTER IX p^^^, j 

Leaves 130-139 ^ 

CHAPTER X \ 

Leaf- Arrangement for Exposure to Sun and Air ; Movk- j 

MENTS OF Leaves and Shoots ...... 140-149 

CHAPTER XI \ 

i 

Minute Structure of Leaves ; Functions of Leaves . . 150-177 

CHAPTER XII , 

Protoplasm and its Properties . . . . . . 178-185 i 

CHAPTER XIII ; 

Inflorescence, or Arrangement of Flowers on the Stem 186-191 ' 

CHAPTER XIV 

The Study of Typical Flowers 192-196 

1 
CHAPTER XV 5 

Plan and Structure of the Flower and its Organs . 197-207 

CHAPTER XVI J 

True Nature of Floral Organs ; Details of their Struc- I 

TURE ; Fertilization 208-216 

CHAPTER XVII I 

The Study of Typical Fruits 217-220 ^ 

1 

CHAPTER XVIII 
The Fruit 221-227 

CHAPTER XIX 
The Classification of Plants 228-234 



CONTENTS 



IX 



CHAPTER XX 
Types of Ckyptogams ; Thallophytes . 



PAGES 

235-276 



CHAPTER XXI 

Types of Cryptogams ; Bryophytes 



277-285 



CHAPTER XXII 
Types of Cryptogams ; Pteridophytes . 



. 286-297 



CHAPTER XXIII 

The Evolutionary History of Plants . 



. 298-305 



LIST OF PLATES 

Frontispiece. Jack-in-tlie-pulpit, a typical shade-plant, with large, .^' 

thin leaves. 

Facing page 
Plate I. Sand-dunes with sea rye grass. Deep-rooted, with exten- 
sively running rootstocks , . . . . . . . 76 ' 

Plate II. Pollarded willows, showing growth of slender twigs from 

adventitious buds 128 

Plate III. Japanese ivy, a tendril-climber growing on face of a 
building, showing leaves all exposed to sunlight at the most 
advantageous angle 140 

Plate IV. Cypress swamp, showing " Spanish moss " {Tillandsia) , 
a phanerogamic epiphyte practically leafless, the work ordinarily 
done by leaves devolving on the slender stems. The cypress 
trees are furnished with " knees " or projections from the roots, 
which are thought by some to absorb air 158 

Plate V. Indian pipe, a saprophytic seed-plant, wholly destitute 

of chlorophyll and with scales instead of foliage leaves . . 168 

Plate VI. Fan palms, showing general habit of the tree, and large 

projecting bases of old petioles left after the decay of the leaves 176 



FOUNDATIONS OF BOTANY 



INTRODUCTION 

" Botany is the science which endeavors to answer every reason- 
able question about plants." ^ 

The plant is a living being, provided generally with 
many parts, called organs^ which it uses for taking in nour- 
ishment, for breathing, for protection against its enemies, 
and for reproducing itself and so keeping up the numbers 
of its own kind. The study of the individual plant there- 
fore embraces a variety of topics, and the examination of 
its relation to others introduces many more subjects. 

Morphology, or the science of form, structure, and so on, 
deals with the plant without much regard to its character 
as a living thing. Under this head are studied the forms 
of plants and the various shapes or disguises which the 
same sort of organ may take in different kinds of plants, 
their gross structure, their microscopical structure, their 
classification, and the successive stages in the develop- 
ment of the individual plant. 

Plant Physiology treats of the plant in action, how it lives, 
breathes, feeds, grows, and produces others like itself. 

Geographical Distribution, or botanical geography, dis- 
cusses the range of the various kinds of plants over the 

1 Professor George L. Goodale. 
1 



2 FOUNDATIONS OF BOTANY 

earth's surface. Another subdivision of botany, usually 
studied along with geology, describes the history of plant 
life on the earth from the appearance of the first plants 
until the present time. 

Systematic Botany, or the classification of plants, should 
naturally follow the examination of the groups of seed- 
plants and spore-plants.. 

Plant Ecology treats of the relations of the plant to 
the conditions under which it lives. Under this division 
of the science are studied the effects of soil, climate, and 
friendly or hostile animals and plants on the external 
form, the internal structure, and the habits of plants. 
This is in many respects the most interesting department 
of botany, but it has to be studied for the most part out 
of doors. 

Many of the topics suggested in the above outline cannot 
well be studied in the high school. There is not usually 
time to take up more than the merest outline of botanical 
geography, or to do much more than mention the impor- 
tant subject of Economic Botany — the study of the uses 
of plants to man. It ought, however, to be possible for 
the student to learn in his high-school course a good deal 
about the simpler facts of morphology and of vegetable 
physiology. One does not become a botanist — not even 
much of an amateur in the subject — by reading books 
about botany. It is necessary to study plants themselves, 
to take them to pieces and make out the connection of their 
parts, to examine with the microscope small portions of the 
exterior surface and thin slices of all the variously built 
materials or tissues of which the plant consists. All this 
can be done with living specimens or with those taken 



INTRODUCTION 3 

from dead parts of plants that have been preserved in any 
suitable way, as by drying or by placing in alcohol or other 
fluids which prevent decay. Living plants must be studied 
in order to ascertain what kinds of food they take, what 
kinds of waste substances they excrete, how and where 
their growth takes place and what circumstances favor it, 
how they move, and indeed to get as complete an idea as 
possible of what has been called the behavior of plants. 

Since the most familiar and most interesting plants 
spring from seeds, the beginner in botany can hardly do 
better than to examine at the outset the structure of a few 
familiar seeds, then sprout them and watch the growth of 
the seedlings which spring from them. Afterwards he 
may study in a few typical examples the organs, structure, 
and functions of seed-plants, trace their life history, and 
so, step by step, follow the process by which a new crop 
of seeds at last results from the growth and development 
of such a seed as that with which he began. 

After he has come to know in a general way about the 
structure and functions of seed-plants, the student may 
become acquainted with some typical cryptogams or spore- 
plants. There are so many groups of these that only a 
few representative ones can be chosen for study. 



Paet I 

STRUCTURE, FUNCTIONS, AND CLASSIFI- 
CATION OF PLANTS 

CHAPTER I 
THE SEED AND ITS GERMINATION 

1. Germination of the Squash Seed. — Soak some squash seeds in 
tepid water for twelve hours or more. Plant these about an inch 
deep in damp sand or pine sawdust or peat-moss in a wooden box 
which has had holes enough bored through the bottom so that it will 
not hold water. Put the box in a warm place (not at any time over 
70° or 80° Fahrenheit)/ and cover it loosely with a board or a pane 
of glass. Keep the sand or sawdust moist, but not wet, and the 
seeds will germinate. As soon as any of the seeds, on being dug up, 
are found to have burst open, sketch one in this condition,^ noting 
the manner in which the outer seed-coat is split, and continue to 
examine the seedlings at intervals of two days, until at least eight 
stages in the growth of the plantlet have been noted. ^ 

1 Here and elsewhere throughout the book temperatures are expressed in 
Fahrenheit degrees, since with us, unfortunately, the Centigrade scale is not 
the familiar one, outside of physical and chemical laboratories. 

2 The student need not feel that he is expected to make finished drawings 
to record what he sees, but some kind of careful sketch, if only the merest 
outline, is indispensable. Practice and study of the illustrations hereafter 
given will soon impart some facility even to those who have had little or no 
instruction in drawing. Consult here Figs. 9 and 89. 

3 The class is not to wait for the completion of this work (which may, if 
desirable, be done by each pupil at home), but is to proceed at once with the 
examination of the squash seed and of other seeds, as directed in the follow- 
ing sections, and to set some beans, peas, and corn to sprouting, so that they 
may be studied at the same time with the germinating squashes. 

5 



FOUNDATIONS OF BOTANY 



m 



a 



}0 cot 



Observe particularly how the sand is pushed aside by the rise of 
the young seedlings. Suggest some reason for the manner in which 
the sand is penetrated by the rising stem. 

2. Examination of the Squash Seed. — 
Make a sketch of the dry seed, natural size. 
Note the little scar at the pointed end of the 
seed where the latter was attached to its 
place of growth in the squash. Label this 
Jiilum. 

Note the little hole in the hilum ; it is 
the micropyle, seen most plainly in a soaked 
seed. (If there are two depressions on the 
hilum the deeper one is the micropyle.) 

Describe the color and textiu'e of the outer 
coating of the seed. With a scalpel or a very 
sharp knife cut across near the middle a seed 
that has been soaked in water for twenty- 
four hours. Squeeze one of the portions, 
held edgewise between the thumb and finger, 
in such a way as to separate slightly the 
halves into which the contents of the seed is 
naturally divided. Examine with the mag- 
nifying glass the section thus treated, make 
a sketch of it, and label the shell or covering 
of the seed and the kernel within this. 

Taking another soaked seed, chip away 
the white outer sheU, called the testay and 
observe the thin, greenish inner skin (Fig. 
1, e), with which the kernel of the seed is 
closely covered.i 

Strip this off and sketch the uncovered ker- 
nel or emhryo. Note that at one end it tapers 
to a point. This pointed portion, known 
as the hypocotyl, will develop after the seed 
sprouts into the stem of the plantlet, like that shown at c in Fig. 2. 
Split the halves of the kernel entirely apart from each other, 

1 See footnote 2 to Sect. 18. 



^---C 



h 

Fig. 1. — Lengthwise Section 
of a Squash Seed. (Magni- 
fied about five times.) 



THE SEED AND ITS GEEMINATION 



noticing that they are only attached for a very little way next to 
the hypocotyl, and observe the thickness of the halves and the slight 
unevenness of the inner surfaces. These halves are called seed-leaves 
or cotyledons. 

Have ready some seeds which have been soaked for twenty-four 
hours and then left in a loosely covered jar on damp blotting paper 
at a temperature of 70° or over 
until they have begun to sprout. 

Split one of these seeds apart, 
separating the cotyledons, and 
observe, at the junction of these, 
two very slender pointed objects, 
the rudimentary leaves of the 
plumule or first bud (Fig. 1, p). 

3. Examination of the Bean. 
— Study the seed, both dry and 
after twelve hours' soaking, in 
the same general way in which 
the squash seed has just been 
examined.^ 

N'otice the presence of a dis- 
tinct plumule, consisting of a pair 
of rudimentary leaves between 
the cotyledons, just where they 
are joined to the top of the hypo- 
cotyl. In many seeds (as the pea) 
the plumule does not show dis- 
tinct leaves. But in all cases 
the plumule contains the growing 
point, the tip of the stem from 
which all the upward growth of 
the plant is to proceed. 

Make a sketch of these leaves as they lie in place on one of the 
cotyledons, after the bean has been split open. 

1 The larger the variety of hean chosen, the easier it will he to see and 
sketch the several parts. The large red kidney hean, the horticultural hean, 
or the lima hean will do well for this examination. 




Fia. 2. 



- The Castor Bean and its 
Germination. 



A, longitudinal section of ripe seed ; t, 
testa; co, cotyledon; c, hypocotyl; 
B, sprouting seed covered with endo- 
sperm ; C, same, with half of endo- 
sperm removed ; D, seedling ; r, pri- 
mary root ; r', secondary roots ; c, arch 
of hypocotyl. 



8 FOUNDATIONS OF BOTANY 

Note the cavity in each cotyledon caused by the pressure of the 
plumule and of the hypocotyl. 

4. Examination of the Pea. — There are no very important points 
of difference between the bean and pea, so far as the structure of 
the seed is concerned, but the student should rapidly dissect a few 
soaked peas to get an idea of the appearance of the parts, since he 
is to study the germination of peas in some detail. 

Make only one sketch, that of the hypocotyl as seen in position 
after the removal of the seed-coats.^ 

5. Germination of the Bean or the White Lupine, the Pea, and tbe 
Grain of Corn. — Soak some beaus or lupine seeds as directed in 
Section 3, plant them,^ and make a series of sketches on the same 
general plan as those in Fig. 9. 

Follow the same directions with some peas and some corn. In the 
case of the corn, make six or more sketches at various stages to illus- 
trate the growth of the plumule and the formation of roots ; first a 
main root from the base of the hypocotyl, then others more slender 
from the same region, and later on still others from points higher 
up on the stem (see Fig. 15). The student may be able to dis- 
cover what becomes of the large outer part of the embryo. This is 
really the single cotyledon of the corn (Fig. 6). It does not as a 
whole rise above ground, but most of it remains in the buried grain, 
and acts as a digesting and absorbing organ through which the 
endosperm or food stored outside of the embryo is transferred into 
the growing plant, as fast as it can be made liquid for that purpose. 

6. Germination of the Horse-Chestnut. — Plant some seeds of the 
horse-chestnut or the buckeye, study their mode of germination, and 
observe the nature and peculiar modifications of the parts. 

Consult Gray's Structural Botany, Vol. I, pp. 19, 20. 

7. Conditions Requisite for Germination. — When we 
try to enumerate the external conditions which can affect 

1 The teacher will find excellent sketches of most of the germinating seeds 
described in tlie present chapter in Miss Newell's Outlines of Lessons in 
Botany, Part I. 

2 The pupil may economize space by planting the new seeds in boxes 
from which part of the earlier planted seeds have been dug up for use in 
sketching, etc. 



THE SEED AND ITS GERMINATION 9 

germination, we find that the principal ones are heat, 
moisture, and presence of air. A few simple experiments 
will show what influence these conditions exert. 

8. Temperature. — Common observation shows that a 
moderate amount of warmth is necessary for the sprout- 
ing of seeds. Every farmer or gardener knows that 
during a cold spring many seeds, if planted, will rot in 
the ground. But a somewhat exact experiment is neces- 
sary to show what is the best temperature for seeds to 
grow in, and whether variations in the temperature make 
more difference in the quickness with which they begin 
to germinate or in the total per cent which finally succeed. 

EXPERIMENT I 

Relation of Temperature to Germination. — Prepare at least four 
teacups or tumblers, each with wet soft paper packed in the bottom 
to a depth of nearly an inch. Have a tightly fitting cover over each. 
Put in each vessel the same number of soaked peas. Stand the ves- 
sels with their contents in places where they will be exposed to dif- 
ferent, but fairly constant, temperatures, and observe the several 
temperatures carefully with a thermometer. Take pains to keep the 
tumblers in the warm places from drying out, so that their contents 
will not be less moist than that of the others. The following series 
is merely suggested, — other values may be found more convenient. 
Note the rate of germination in each place and record in tabular 
form as follows : 

No. of seeds sprouted in 24 hrs. 48 hrs. 72 hrs. 96 hrs. etc. 

At 32°, 

At 50°, 

At 70°, 

At90°,i — 

1 For the exact regulation of the temperatures a thermostat (see Handbook) 
is desirable. If one is available, a maximum temperature of 100° or over 
should be tried. 



10 



EOUNDATIONS OF BOTANY 



9. Moisture. — What was said in the preceding section 
in regard to temperature applies also to the question of 
the best conditions for germination as regards the supply 
of moisture. The soil in which seeds grow out of doors 
is always moist; it rests with the experimenter to find 
out approximately what is the best amount of moisture. 



EXPERIMEl^T III 

Relation of Water to Germination. — Arrange seeds in several 
vessels as follows : 

In the first put blotting paper that is barely moistened ; on this 
put some dry seeds. 

In the second put blotting paper that has been barely moistened ; 
on this put seeds that have been soaked for twenty-four hours. 

In the third put 
water enough to soak 
the paper thor- 
oughly; use soaked 
seeds. 

In the fourth put 
water enough to half 
cover the seeds. 

Place the vessels 
where they will have 
same temperature and 
note the time of ger- 
mination. 

Tabulate your re- 
sults as in the previ- 
ous experiment. 

10. Relation of the Air Supply to Germination. — If we 

wish to see how soaked seeds will behave with hardly any 
air supply, it is necessary to place them in a bottle arranged 

1 This may be made a home experiment. 




Fig. 3. — Soaked Peas in Stoppered Bottle, ready 
for Exhaustion of Air. 



THE SEED AND ITS GERMINATION 11 

as shown in Fig. 3, exhaust the air by connecting the glass 
tube with an air-pump, which is then pumped vigorously, 
and seal the tube while the exhaustion is going on. The 
sealing is best done by holding a Bunsen flame under the 
middle of the horizontal part of the tube. A much easier 
experiment, which is nearly as satisfactory, can, however, 
be performed without the air-pump. 

EXPERIMENT III 

Will Seeds Germinate well without a Good Supply of Air ? — 

Place some soaked seeds on damp blotting paper in the bottom of a 
bottle, using seeds enough to fill it three-quarters full, and close 
tightly with a rubber stopper. 

Place a few other seeds of the same kind in a second bottle ; 
cover loosely. 

Place the bottles side by side, so that they will have the same 
conditions of light and heat. Watch for results, and tabulate as in 
previous experiments. 

Most seeds will not germinate under water, but those of the 
sunflower wiU. do so, and therefore Exp. Ill may be varied in the 
following manner : 

Remove the shells carefully from a considerable number of sun- 
flower seeds. ^ Try to germinate one lot of these in water which has 
been boiled in a flask to remove the air, and then cooled in the 
• same flask. Over the water, with the seeds in it, a layer of cotton- 
seed oil about a half inch deep is pom-ed, to keep the water from 
contact with air. In this bottle then there will be only seeds and 
air-free water. Try to germinate another lot of seeds in a bottle 
half filled with ordinary water, also covered with cotton-seed oil. 
Results ? 

11. Germination involves Chemical Changes. — If a ther- 
mometer is inserted into a jar of sprouting seeds, for 

1 These are really fruits, but the distinction is not an important one at 
this time. 



12 FOUNDATIONS OF BOTANY 

instance peas, in a room at the ordinary temperature, the 
peas will be found to be warmer than the surrounding 
air. This rise of temperature is at least partly due to 
the absorption from the air of that substance in it which 
supports the life of animals and maintains the burning of 
fires, namely, oxygen. 

The union of oxygen with substances with which it 
can combine, that is with those which will burn, is called 
oxidation. This kind of chemical change is universal in 
plants and animals while they are in an active condition, 
and the energy which they manifest in their growth and 
movements is as directly the result of the oxidation going 
on inside them as the energy of a steam engine is the 
result of the burning of coal or other fuel under its boiler. 
In the sprouting seed much of the energy produced by 
the action of oxygen upon oxidizable portions of its con- 
tents is expended in producing growth, but some of this 
energy is wasted by being transformed into heat which 
escapes into the surrounding soil. It is this escaping 
heat which is detected by a thermometer thrust into a 
quantity of germinating seeds. 

EXPERIMENT IV 

Effect of Germinating Seeds upon the Surrounding Air. — When 
Exp. Ill has been finished, remove a little of the air from above the 
peas in the first bottle. This can easily be done with a rubber bulb 
attached to a short glass tube. Then bubble this air through some 
clear, filtered limewater. Also blow the breath through some lime- 
water by aid of a short glass tube. Explain any similarity in 
results obtained. (Carbon dioxide turns limewater milky.) After- 
wards insert into the air above the peas in the same bottle a lighted 
pine splinter, and note the effect upon its flame. 



THE SEED AND ITS GERMINATION 13 

12. Other Proofs of Chemical Action. — Besides the proof 
of chemical changes in germinating seeds just described, 
there are other kinds of evidence to the same effect. 

Malt, which is merely sprouted barley with its germi- 
nation permanently stopped at the desired point by the 
application of heat, tastes differently from the unsprouted 
grain, and can be shown by chemical tests to have suffered 
a variety of changes. If you can get unsprouted barley 
and malt, taste both and see if you can decide what sub- 
stance is more abundant in the malt. 

Germinating kernels of corn undergo great alterations 
in their structure ; the starch grains are gradually eaten 
away until they are ragged and full of holes and finally 
disappear. 

13. The Embryo and its Development. — The miniature 
plant, as it exists ready formed and alive but inactive in 
the seed, is called the embryo. In the seeds so far ex- 
amined, practically the entire contents of the seed-coats 
consist of the embryo, but this is not the case with the 
great majority of seeds, as will be shown in the following 
chapter. 



CHAPTER II 



STORAGE OF FOOD IN THE SEED 



14. Food in the Embryo. — Squash seeds are not much 
used for human food, though both these and melon seeds 
are occasionally eaten in parts of Europe ; but beans and 
peas are important articles of food. Whether the material 
accumulated in the cotyledons is an aid to the growth of 
the young plant may be learned from a simple experiment. 

15. Mutilated and Perfect Seedlings. — One of the best 
ways in which to find out the importance and the special 

use of any part of 
a plant is to re- 
move the part in 
question and see 
how the plant be- 
haves afterward. 




EXPERIMENT V^ 




Fig. 4. 



Are the Cotyledons 
of a Pea of any Use 
to the Seedling ? — 

Sprout several peas on 
blotting paper. When 
the plumules appear, 
carefully cut away the cotyledons from some of the seeds. Place on 
a perforated cork, as shown in Fig. 4, one or two seedlings from 

1 May be a home experiment. 
14 



■ Germinating Peas, growing in Water, one 
deprived of its Cotyledons. 



STORAGE OF EOOD IN THE CELLS 15 

which the cotyledons have been cut, and as many which have not 
been mutilated, and allow the roots to extend into the water. Let 
them grow for some days, or even weeks, and note results. 

16. Food stored in Seeds in Relation to Growth after 

Germination If two kinds of seeds of somewhat similar 

character, one kind large and the other small, are allowed 
to germinate and grow side by side, some important infer- 
ences may be drawn from their relative rate of growth. 

EXPERIMEi^T VII 

Does the Amount of Material in the Seed have anything to do with 
the Rate of Growth of the Seedling ? — Germinate ten or more 
clover seeds, and about the same number of peas, on moist blotting 
paper under a bell-jar. After they are well sprouted, transfer both 
kinds of seeds to fine cotton netting, stretched across wide-mouthed 
jars nearly full of water. The roots should dip into the water, but 
the seeds must not do so. Allow the plants to grow until the peas 
are from four to six inches high. 

Some of the growth in each case depends on material 
gathered from the air and water, but most of it, during the 
very early life of the plant, is due to the reserve material 
stored in the seed. Where is it in 
the seeds so far studied ? Proof ? 

17. Storage of Food outside of 
the Embryo. — In very many cases 
the cotyledons contain little food, j n 

but there is a supply of it stored fig. 5. — seeds mth Endosperm, 
,, 1 T • 1 1 J^ Longitudinal Sections. 

m the seed beside or around them 

I, asparagus (magnified). 
(Figs. 2, 5, and 6). 11, poppy (magnified). 

18. Examination of the Four-o'clock Seed. — Examine the exter- 
nal surface of a seed ^ of the four-o'clock, and try the hardness of 

1 May be a home experiment. 2 strictly speaking, a fruit. 





16 



FOUNDATIONS OF BOTANY 



the outer coat by cutting it with a knife. From seeds which hava 
been soaked in water at least twenty-four hours peel off the coatings 
and sketch the kernel. Make a cross-section of one of the soaked 
seeds which has not been stripped of its coatings, and sketch the sec- 
tion as seen with the magnifying glass, to show the parts, especially 
the two cotyledons, lying in close contact and encircling the white, 
starchy-looking endosperm.^ 

The name endosperm is applied to food stored in parts of the 
seed other than the embryo.^ With a mounted needle pick out the 
little almost spherical mass of endosperm from inside the cotyledons 
of a seed which has been deprived of 
its coats, and sketch the embryo, noting 
how it is curved so as to enclose the 
endosperm almost completely. 

19. Examination of the Kernel of In- 
dian Corn. — Soak some grains of large 
yellow field corn ^ for about three days. 

Sketch an unsoaked kernel, so as to 
show the grooved side, where the germ 
lies. Observe how this groove has be- 
come partially filled up in the soaked 
kernels. 

Remove the thin, tough skin from 
one of the latter, and notice its transpar- 
ency. This skin — the bran of unsifted 
corn meal — does not exactly correspond 
to the testa and inner coat of ordinary 
seeds, since the kernel of corn, like all 
other grains (and like the seed of the 
four-o'clock), represents not merely the seed, but also the seed-vessel 
in which it was formed and grew, and is therefore a fruit. 

1 Buckwheat furnishes another excellent study in seeds with endosperm. 
Like that of the four-o'clock, it is, strictly speaking, a fruit ; so also is a grain 
of corn. 

2 In the squash seed the green layer which covered the embryo represents 
the remains of the endosperm. 

3 The varieties with long, flat kernels, raised in the Middle and Southern 
States under the name of " dent corn," are the best. 




--P 



-r 



Fig. 6. — Lengthwise Section of 

Grain of Corn. (Magnified 

about three times.) 

1/, yellow, oily part of endosperm ; 
w, white, starchy part of en- 
dosperm ; p, plumule ; s, the 
shield (cotyledon), in contact 
with the endosperm for abs9rp- 
tion of food from it ; r, the 
primary root. 



STORAGE OF FOOD IN THE SEED 17 

Cut sections of the soaked kernels, some transverse, some length- 
wise and parallel to the flat surfaces, some lengthwise and at right 
angles to the flat surfaces. Try the effect of staining some of these 
sections with iodine solution. 

Make a sketch of one section of each of the three kinds, and label 
the dirty white portion, of cheesy consistency, embryo ; and the yel- 
low portions, and those which are white and floury, endosperm. 

Chip off the endosperm from one kernel so as to remove the 
embryo free from other parts.^ Notice its form, somewhat triangular 
in outline, sometimes nearly the shape of a beechnut, in other speci- 
mens nearly like an almond. 

Estimate what proportion of the entire bulk of the soaked kernel 
is embryo. 

Split the embryo lengthwise so as to show the slender, somewhat 
conical plumule. ^ 

20. Corn Seedlings deprived of Endosperm — An experi- 
ment parallel to No. V serves to show the function and 
the importance of the endosperm of Indian corn. 

EXPERIMENT VII 

Of how much Use to the Corn Seedling is the Endosperm ? — Sprout 
kernels of corn on blotting paper. When they get fairly started, 
cut away the endosperm carefully from several of the seeds. Sus- 
pend on mosquito netting on the surface of water in the same jar 
two or three seedlings which have had their endosperm removed, and 
as many which have not been mutilated. Let them grow for some 
weeks, and note results. 

21. Starch. — Most common seeds contain starch. < 
Every one knows something about the appearance of ordi- 

1 The embryo may be removed with great ease from kernels of rather ma- 
ture green corn. Boil the corn for about twenty minutes on the cob, then pick 
the kernels off one by one with the point of a knife. They may be preserved 
indefinitely in alcohol of 50 or 75%. 

2 The teacher may well consult Figs. 56-61, inclusive, in Gray's Structural 
Botany. 



18 rOUNDATIONS OF BOTANY 

nary commercial starch as used in the laundry, and as 
sold for food in packages of cornstarch. When pure it 
is characterized not only by its lustre, but also by its 
peculiar velvety feeling when rubbed between the fingers. 

22. The Starch Test It is not always easy to recog- 
nize at sight the presence of starch as it occurs in seeds, 
but it may be detected by a very simple chemical test, 
namely, the addition of a solution of iodine.^ 

EXPERIMEN^T VIII 2 

Examination of Familiar Seeds with Iodine. — Cut in two with a 
sharp knife the seeds to be experimented on, then pour on each, drop 
by drop, some of the iodine solution. Only a little is necessary; 
sometimes the first drop is enough. 

If starch is present, a blue color (sometimes almost black) will 
appear. If no color is obtained in this way, boil the pulverized 
seeds for a moment in a few drops of water, and try again. 

Test in this manner corn, wheat (in the shape of flour), oats (in 
oatmeal), barley, rice, buckwheat, flax, rye, sunflower, four-o'clock, 
morning-glory, mustard seed, beans, peanuts. Brazil-nuts, hazelnuts, 
and any other seeds that you can get. Report your results in tabu- 
lar form as follows : 

Much Starch Little Starch No Starch 

Color : blackish or Color : pale blue or Color : brown, orange, 
dark blue. greenish. or yellowish. 

23. Microscopical Examination of Starch.^ — Examine starch in 
^ water with a rather high power of the microscope (not less than 200 

diameters). 

1 The tincture of iodine sold at the drug-stores will do, but the solution 
prepared as directed in the Handbook answers better. This may be made up 
in quantity, and issued to the pupils in drachm vials, to be taken home and 
used there, if the experimenting must be done outside of the laboratory or the 
schoolroom. 2 ]\f ^y be a home experiment. 

3 At this point the teacher should give a brief illustrated talk on the con- 
struction and theory of the compound microscope. 



STOEAGE OF FOOD IN THE SEED 



19 



PiiJp scraped from a potato, that from a canna rootstock, wheat 
flour, the finely powdered starch sold under the commercial name of 
"cornstarch" for cookmg, oat- 
meal, and buckwheat finely pow- 
dered in a mortar, will furnish 
excellent examples of the shape 
and markings of starch grains. 
Sketch all of the kinds exam- 
ined, taking pains to bring out 
the markings.! Compare the 
sketches with Figs. 7 and 8. 

With a medicine-dropper or a 
very small pipette run in a drop 
of iodine solution under one edge 
of the cover-glass, at the same time withdrawing a little water from 
the margin opposite by touching to it a bit of blotting paper. 




Fig. 7. — Canna Starch. (Magnified 
300 diameters.) 



qu- 

sch- 

br-' 




Fig. 8. — Section through Exterior Part of a Grain of Wheat. 
c, cuticle or outer layer of bran ; ep, epidermis ; m, layer beneath epidermis ; qu, 
sch, layers of hull next to seed-coats ; br, n, seed-coats ; Kl, layer containing 
proteid grains ; st, cells of the endosperm filled with starch. (Greatly magnified. ) 

1 The markings will be seen more distinctly if care is taken not to admit 
too much light to the object. Rotate the diaphragm beneath the stage of the 
microscope, or otherwise regulate the supply of light, until the opening is 
found which gives the best effect. 



20 FOUNDATIONS OF BOTANY ! 

i 

Examine again and note the blue coloration of the starch grains and 
the unstained or yellow appearance of other substances in the field. ' 
Cut very thin slices from beans, peas, or kernels of corn ; mount in ■ 
water, stain as above directed, and draw as seen under the microscope. \ 
Compare with Figs. 7 and 8.^ Note the fact that the starch is not i 
packed away in the seeds in bulk, but that it is enclosed in little J 
chambers or cells. : 

24. Plant-Cells. — Almost all the parts of the higher ' 
plants are built up of little separate portions called cells. \ 
The cell is the unit of plant-structure, and bears some- 1 
thing the same relation to the plant of which it is a part I 
that one cell of a honeycomb does to the whole comb. 
But this comparison is not a perfect one, for neither the ; 
waxen wall of the honeycomb-cell nor the honey within it 1 
is alive, while every plant-cell is or has been alive. And ^ 
even the largest ordinary honeycomb consists of only a j 
few hundred cells, while a large tree is made up of very | 
many miillons of cells. The student must not conceive S 
of the cell as merely a little chamber or enclosure. The ; 
living, more or less liquid, or mucilage-like, or jelly-like \ 
substance known as protoplasm, which forms a large portion 
of the hulk of living and growing cells, is the all-important 
part of such a cell. Professor Huxley has well called 
this substance " the physical basis of life." Cells are of \ 
all shapes and sizes, from little spheres a ten-thousandth I 
of an inch or less in diameter to slender tubes, such as 
fibers of cotton, several inches long. To get an idea of 
the appearance of some rather large cells, scrape a little 
pulp from a ripe, mealy apple, and examine it first with 

1 The differentiation between the starch grains, the other cell-contents, 
and the cell-walls will appear better in the drawings if the starch grains are 
sketched with blue ink. 



STORAGE OF FOOD IN THE SEED 21 

a strong magnifying glass, then with a moderate power of 
the compound microscope. To see how dead, dry cell- 
walls, with nothing inside them, look, examine (as before) 
a very thin slice of elder pith, sunflower pith, or pith from 
a dead cornstalk. Look also at the figures in Chapter VI 
of this book. Notice that the simplest plants (Chapter XX) 
consist of a single cell each. The study of the structure 
of plants is the study of the forms which cells and groups 
of cells assume, and the study of plant physiology is the 
study of what cells and cell combinations do. 

25. Absorption of Starch from the Cotyledons. — Examine with 
the microscope, using a medium power, soaked beans and the cotyle- 
dons from seedlings that have been growing for three or four weeks- 
Stain the sections with iodine solution, and notice how completely 
the clusters of starch grains that filled most of the cells of the un- 
sprouted cotyledons have disappeared from the shriveled cotyledons 
of the seedlings. A few grains may be left, but they have lost their 
sharpness of outline. 

26. Oil. — The presence of oil in any considerable 
quantity in seeds is not as general as is the presence of 
starch, though in many common seeds there is a good 
deal of it. 

Sometimes the oil is sufficiently abundant to make it 
worth while to extract it by pressure, as is done with flax- 
seed, cotton-seed, the seeds of some plants of the cress 
family, the " castor bean," and other seeds. 

27. Dissolving Oil from Ground Seeds. — It is not possi- 
ble easily to show a class how oil is extracted from seeds 
by pressure ; but there are several liqu.ids which readily 
dissolve oils and yet have no effect on starch and most of 
the other constituents of seeds. 



22 FOUNDATIONS OF BOTANY 



EXPERIMENT IX 

Extraction of Oil by Ether or Benzine. — To a few ounces of 
ground flaxseed add an equal volume of ether or benzine. Let it 
stand ten or fifteen minutes and then filter. Let the liquid stand in 
a saucer or evaporating dish in a good draught till it has lost the 
odor of the ether or benzine. 

Describe the oil which you have obtained. 

Of what use would it have been to the plant ? 

If the student wishes to do this experiment at home for himself, 
he should bear in mind the following : 

Caution. — Never handle benzine or ether near a flame or stove. 

A much simpler experiment to find oil in seeds may readily be 
performed by the pupil at home. Put the material to be studied, e.g., 
flaxseed meal, corn meal, wheat flour, cotton-seed meal, buckwheat 
flour, oatmeal, and so on, upon little labeled pieces of white paper, 
one kind of flour or. meal on each bit of paper. Place all the papers, 
with their contents, on^a perfectly clean plate, free from cracks, or 
on a clean sheet of iron, and put this in an oven hot enough nearly 
(but not quite) to scorch the paper. After half an hour remove the 
plate from the oven, shake off the flour or meal from each paper, and 
note the results, a more or less distinct grease spot showing the 
presence of oil, or the absence of any stain that there was little or 
no oil in the seed examined. 

28. Albuminous Substances. — Albuminous substances 
or proteids occur in all seeds, though often only in small 
quantities. They have nearly the same chemical compo- 
sition as white of egg and the curd of milk among animal 
substances, and are essential to the plant, since the living 
and growing parts of all plants contain large quantities of 
proteid material. 

Sometimes the albuminous constituents of the seed occur 
in more or less regular grains (Fig. 8, at Kl) . 

But much of the proteid material of seeds is not in any 



STORAGE OF FOOD IN THE SEED 23 

form in which it can be recognized under the microscope. 
One test for its presence is the peculiar smell which it 
produces in burning. Hair, wool, feathers, leather, and 
lean meat all produce a well-known sickening smell when 
scorched or burned, and the similarity of the proteid mate- 
rial in such seeds as the bean and pea to these substances 
is shown by the fact that scorching beans and similar 
seeds give off the familiar smell of burnt feathers. 

29. Chemical Tests for Proteids. — All proteids (and 
very few other substances) are turned yellow by nitric 
acid, and this yellow color becomes deeper or even orange 
when the yellowish substance is moistened with ammonia. 
They are also turned yellow by iodine solution. Most 
proteids are turned more or less red by the solution of 
nitrate of mercury known as Millon's reagent.^ 

EXPERIMENT X 

Detection of Proteids in Seeds. — Extract the germs from some 
soaked kernels of corn and bruise them; soak some wheat-germ meal 
for a few hours in warm water, or wash the starch out of wheat- 
flour dough ; reserving the latter for use, place it in a white saucer or 
porcelain evaporating dish, and moisten well with Millon's reagent 
or with nitric acid ; examine after fifteen minutes. 

30. The Brazil-Nut as a Typical Oily Seed. — Not many 
familiar seeds are as oily as the Brazil-nut. Its large size 
makes it convenient for examination, and the fact that this 
nut is good for human food makes it the more interesting 
to investigate the kinds of plant-food which it contains. 

1 See Handbook. 



24 



FOUNDATIONS OF BOTANY 



EXPEB,IMENT XI 



Testing Brazil-Nuts for Plant-Foods. — Crack fifteen or twenty 
Brazil-nuts, peel of£ the brown coating from the kernel of each, and 
then grind the kernels to a pulp in a mortar. Shake up this pulp 
with ether, pour upon a paper filter, and wash with ether until the 
washings when evaporated are nearly free from oil. The funnel 
containing the filter should be kept covered as much as possible 
until the washing is finished. Evaporate the filtrate to procure the 
oil, which may afterwards be kept in a glass-stoppered bottle. Dry 
the powder which remains on the filter and keep it in a wide- 
mouthed bottle. Test portions of this powder for proteids and for 
starch. Explain the results obtained. 

31. Other Constituents of Seeds. — Besides the substances 
above suggested, others occur in different seeds. Some 
of these are of use in feeding the seedling, others are of 
value in protecting the seed itself from being eaten by 
animals or in rendering it less liable to decay. In such 
seeds as that of the nutmeg, the essential oil which gives 
it its characteristic flavor probably makes it unpalatable 
to animals and at the same time preserves it from decay. 

Date seeds are so hard and tough that they cannot be 
eaten and do not readily decay. Lemon, orange, horse- 
chestnut and buckeye seeds are too bitter to be eaten, and 
the seeds of the apple, cherry, peach, and plum are some- 
what bitter. 

The seeds of larkspur, thorn-apple,^ croton, the castor- 
oil plant, nux vomica, and many other kinds of plants 
contain active poisons. 

1 Datura, commonly called " Jimpsou weed." 



CHAPTER III 

MOVEMENTS, DEVELOPMENT, AND MORPHOLOGY OF 
THE SEEDLING 



32. How the Seedling breaks Ground. — As the student 
has already learned by his own observations, the seedling 
does not always push its way straight out of the ground. 
Corn, like all the other grains and grasses, it is true, sends 
a tightly rolled, pointed leaf vertically upward into the 
air. But the other seedlings examined usually will not 
be found to do anything of the sort. The squash seedling 
is a good one in which to study what may 
be called the arched hypocotyl 
type of germination. If the ^^ c:^^^ 
seed when planted is laid hori- 



^^, 




A B C D E 

Fig. 9. — Successive Stages in the Life History of the Squash Seedling. 

GG, the surface of the ground ; r, primary root ; r', secondary root ; c, hypocotyl ; 
a, arch of hypocotyl ; co, cotyledons. 

zontally on one of its broad surfaces, it usually goes through 
some such changes of position as are shown in Fig. 9. 

26 



26 FOUNDATIONS OF BOTANY 

The seed is gradually tilted until, at the time of their 
emergence from the ground (at (7),- the cotyledons are 
almost vertical. The only part above the ground-line (7, 6r, 
at this period, is the arched hypocotyl. Once out of ground, 
the cotyledons soon rise, until (at JE) they are again ver- 
tical, but with the other end up from that which stood 
highest in C. Then the two cotyledons separate until 
they once more lie horizontal, pointing away from each 
other. 

Can you suggest any advantage which the plant derives 
from having the cotyledons dragged out of the ground 
rather than having them pushed out, tips first? 

33. Cause of the Arch. — It is evident that a flexible 
object like the hypocotyl, when pushed upward through the 
earth, might easily be bent into an arch or loop. Whether 
the shape which the hypocotyl assumes is wholly caused 
by the resistance of the soil can best be ascertained by 
an experiment. 

EXPERIMENT XII 

Is the Arch of the Hypocotyl due to the Pressure of the Soil on the 
Rising Cotyledons ? — Sprout some squash seeds on wet paper under 
a bell-glass, and when the root is an inch or more long, hang several 
of the seedlings, roots down, in little stirrups made of soft twine, 
attached by beeswax and rosin mixture to the inside of the upper 
part of a bell-glass. Put the bell-glass on a large plate or a sheet of 
glass on which lies wet paper to keep the air moist. Note whether 
the seedlings form hypocotyl arches at all and, if so, whether the 
arch is more or less perfect than that formed by seedlings growing 
in earth, sand, or sawdust. 

34. What pushes the Cotyledons up? — A very little 
study of any set of squash seedlings, or even of Fig. 9, is 



MORPHOLOGY OF THE SEEDLING 27 

sufficient to show that the portion of the plant where 
roots and hypocotyl are joined neither rises nor sinks, but 
that the plant grows both ways from this part (a little 
above r' in Fig. 9, A and B). It is evident that as soon as 
the hypocotyl begins to lengthen much it must do one of 
two things : either push the cotyledons out into the air or 
else force the root down into the ground as one might 
push a stake down. What changes does the plantlet 
undergo, in passing from the stage shown at A to that 
of B and of 6^, making it harder and harder for the root 
to be thrust downward? 

35. Use of the Peg. — Squash seedlings usually (though 
not always) form a sort of knob on the hypocotyl. This is 
known as the peg. Study a good many seedlings and try 
to find out what the lengthening of the hypocotyl, between 
the peg and the bases of the cotyledons, does for the little 
plant. Set a lot of squash seeds, hilum down, in moist 
sand or sawdust and see whether the peg is more or less 
developed than in seeds sprouted lying on their sides, and 
whether the cotyledons in the case of the vertically planted 
seeds usually come out of the ground in the same condi- 
tion as do those shown in Fig. 9. 

36. Discrimination between Root and Hypocotyl. — It is 
*not always easy to decide by their appearance and be- 
havior what part of the seedling is root and what part is 
hypocotyl. In a seedling visibly beginning to germinate, 
the sprout, as it is commonly called, which projects from 
the seed might be either root or hypocotyl or might consist 
of both together, so far as its appearance is concerned. A 
microscopic study of the cross-section of a root, compared 
with one of the hypocotyl, would show decided differences 



28 FOUNDATIONS OF BOTANY 

of structure between the two. Their mode of growth is 
also different, as the pupil may infer after he has tried 
Exp. XIV. 

37. Discrimination by Staining. — For some reason, per- 
haps because the skin or epidermis of the young root is 
not so water-proof as that of the stem, the former stains 
more easily than the latter does. 

EXPERIMENT XIII 

The Permanganate Test. — Make a solution of potassium perman- 
ganate in water, by adding about four parts, by weight, of the crystal- 
lized permanganate to 100 parts of water. Drop into the solution 
seedlings, e.g., of all the kinds that have been so far studied, each in 
its earliest stage of germination (that is, when the root or hypocotyl 
has pushed out of the seed half an inch or less), and also at one or 
two subsequent stages. After the seedlings have been in the solu- 
tion from three to five minutes, or as soon as the roots are consider- 
ably stained, pour off (and save) the solution and rinse the plants 
with plenty of clear water. Sketch one specimen of each kind, col- 
oring the brown-stained part, which is root, in some way so as to 
distinguish it from the unstained hypocotyl. Note particularly how 
much difference there is in the amount of lengthening in the several 
kinds of hypocotyl examined. Decide whether the peg of the squash 
seedling is an outgrowth of hypocotyl or of root. 

38. Disposition made of the Cotyledons. — As soon as 
the young plants of squash, bean, and pea have reached 
a height of three or four inches above the ground it is 
easy to recognize important differences in the way in 
which they set out in life. 

The cotyledons of the squash increase greatly in sur- 
face, acquire a green color and a generally leaf-like appear- 
ance, and, in fact, do the work of ordinary leaves. In 



MORPHOLOGY OF THE SEEDLING 29 

such a case as this the appropriateness of the name seed- 
leaf is evident enough, — one ]'ecognizes at sight the fact 
that the cotyledons are actually the plant's first leaves. 
In the bean the leaf-like nature of the cotyledons is not 
so clear. They rise out of the ground like the squash 
cotyledons, but then gradually shrivel away, though they 
may first turn green and somewhat leaf-like for a time. 
* In the pea (as in the acorn, the horse-chestnut, and 
many other seeds) we have quite another plan, the under- 
ground type of germination. Here the thick cotyledons 
no longer rise above ground at all, because they are so 
gorged with food that they could never become leaves ; 
but the young stem pushes rapidly up from the surface 
of the soil. 

The development of the plumule seems to depend some- 
what on that of the cotyledons. The squash seed has 
cotyledons which are not too thick to become useful leaves, 
and so the plant is in no special haste to get ready any 
other leaves. The plumule, therefore, cannot be found 
with the magnifying glass in the unsprouted seed, and is 
almost microscopic in size at the time when the hypocotyl 
begins to show outside of the seed-coats. 

In the bean and pea, on the other hand, since tlie cotyle- 
dons cannot serve as foliage leaves, the later leaves must 
be pushed forward rapidly. In the bean the first pair are 
already well formed in the seed. In the pea they cannot 
be clearly made out, since the young plant forms several 
scales on its stem before it produces any full-sized leaves, 
and the embryo contains only hypocotyl, cotyledons, and a 
sort of knobbed plumule, well developed in point of size, 
representing the lower scaly part of the stem. 



30 FOUNDATIONS OF BOTANY 

39. Root, Stem, and Leaf. — By the time the seedling is 
well out of the ground it, in most cases, possesses the three 
kinds of vegetative organs, or parts essential to growth, of 
ordinary flowering plants, i.e., the root, stem, and leaf, or, 
as they are sometimes classified, root and shoot. All of 
these organs may multiply and increase in size as the 
plant grows older, and their mature structure will be 
studied in later chapters, but some facts concerning them 
can best be learned by watching their growth from the 
outset. 

40. Young Roots grown for Examination. — Roots grow- 
ing in sand or ordinary soil cling to its particles so tena- 
ciously that they cannot easily be studied, and those grown 
in water have not quite the same form as soil-roots. Roots 
grown in damp air are best adapted for careful study. 

41. Elongation of the Root. — We know that the roots 
of seedlings grow pretty rapidly from the fact that each 
day finds them reaching visibly farther down into the 
water or other medium in which they are planted. A 
sprouted Windsor bean in a vertical thistle-tube will send 
its root downward fast enough so that ten minutes' watch- 
ing through the microscope will suffice to show growth. 
To find out just where the growth goes on requires a 
special experiment. 

EXPERIMENT XIV 

In what Portions of the Root does its Increase in Length take Place ? 

— Sprout some peas on moist blotting paper in a loosely covered tum- 
bler. When the roots are one and a half inches or more long, mark 
them along the whole length with little dots made with a bristle 
dipped in water-proof India ink, or a fine inked thread stretched on 
a little bow of whalebone or brass wire. 



MORPHOLOGY OF THE SEEDLING 31 

Transfer the plants to moist blotting paper under a bell-glass or 
an inverted battery jar and examine the roots at the end of twenty- 
four hours to see along what portions their length has increased ; 
continue observations on them for several days. 

42. Root-Hairs. — Barley, oats, wheat, red clover, or 
buckwheat seeds soaked and then sprouted on moist 
blotting paper afford convenient material for studying 
root-Tiairs. The seeds may be kept covered with a watch- 
glass or a clock-glass while sprouting. After they have 
begun to germinate well, care must be taken not to 
have them kept in too moist an atmosphere, or very few 
root-hairs will be formed. Examine with the magni- 
fying glass those parts of the root which have these 
appendages. 

Try to find out whether all the portions of the root are 
equally covered with hairs and, if not, where they are 
most abundant. (See also Sect. 53.) 

The root-hairs in plants growing under ordinary condi- 
tions are surrounded by the moist soil and wrap them- 
selves around microscopical particles of earth (Fig. 11). 
Thus they are able rapidly to absorb through their thin 
walls the soil- water, with whatever mineral substances it 
has dissolved in it. 

43. The Young Stem. — The hypocotyl, or portion of 
the stem which lies below the cotyledons, is the earliest 
formed portion of the stem. Sometimes this lengthens but 
little ; often, however, as the student knows from his own 
observations, the hypocotyl lengthens enough to raise the 
cotyledons well above ground, as in Fig. 10. 

The later portions of the stem are considered to be 
divided into successive nodes, — places at which a leaf (or 



32 



FOUNDATIONS OF BOTANY 



a scale which represents a leaf) appears; and internodes, — - 
portions between the leaves. 

The student should watch the growth of a seedling 
bean or pea and ascertain by actual measurements whether 
the internodes lengthen after they have once been formed, 
and if so, for how long a time the increase continues. 





Fig. 10. 



Fia. 11. 



Fig. 10. — A Turnip Seedling, with, the Cotyledons developed into Temporary Leaves. 
h, root-hairs from the primary root ; b, bare portion of the root, on which, no 
hairs have as yet been produced. 

Fig. 11. — Cross-Section of a Koot, a good deal magnified, showing root-hairs attached 
to particles of soil, and sometimes euAvrapping these particles. 



44. The First Leaves. — The cotyledons are, as already 
explained, the first leaves which the seedling possesses, — 
even if a plumule is found well developed in the seed, it 
was formed after the cotyledons. In those plants which 
have so much food stored in the cotyledons as to render 
these unfit ever to become useful foliage leaves, there is 
little or nothing in the color, shape, or general appearance 



MOKPHOLOGY OF THE SEEDLING 33 

of the cotyledon to make one think it really a leaf, and it 
is only by studying many cases that the botanist is enabled 
to class all cotyledons as leaves in their nature, even if they 
are quite unable to do the ordinary work of leaves. The 
study of the various forms which the parts or organs of a 
plant may assume is called morphology ; it traces the rela- 
tionship of parts which are really akin to each other, 
though dissimilar in appearance and often in function. 
In seeds which have endosperm^ or food stored outside of 
the embryo, the cotyledons usually become green and 
leaf-like, as they do, for example, in the four-o'clock, the 
morning-glory, and the buckwheat ; but in the seeds of 
the grains (which contain endosperm) a large portion of 
the single cotyledon remains throughout as a thickish 
mass buried in the seed. In a few cases, as in the pea, 
there are scales instead of true leaves formed on the first 
nodes above the cotyledons, and it is only at about the 
third node above that leaves of the ordinary co 

kind appear. In the bean and some other 
plants which in general bear one leaf at a 
node along the stem, there is a pair produced 
at the first node above the cotyledons, and 
the leaves of this pair differ in shape from 
those which arise from the succeeding por- 
tions of the stem. 

45. Classification of Plants by the Number 
of their Cotyledons. — In the pine family the fi^,. jo -oer 
germinating seed often displays more than minating Pme. 
two cotyledons, as shown in Fig. 12; in the ^^' ««tyi«^<>^^- 
majority of common flowering plants the seed con- 
tains two cotyledons, while in the lilies, the rushes, the 




(, 



34 



FOUNDATIONS OF BOTANY 



sedges, the grasses, and some other plants, there is but one 
cotyledon. Upon these facts is based the division of most 
flowering plants into two great groups : the dicotyledonous 
plants^ which have two seed-leaves, and the monocotyledon- 
ous plants, which have one seed-leaf. Other important 
differences nearly always accompany the difference in 
number of cotyledons, as will be seen later. 

46. Tabular Review of Experiments. — Make out a 
table containing a very brief summary of the experiments 
thus far performed, as follows : 



Number 

OF 

Experiment 



Object 

SOUGHT 



Materials 

AND 

Apparatus 



Opera- 
tions 
performed 



Results 



Inferences 



47. Review Sketches. — - Make out a comparison of the 
early life histories of all the other seedlings studied, by 
arranging in parallel columns a series of drawings of each, 



MORPHOLOGY OF THE SEEDLING 



35 



like those of Fig. 9, but in vertical series, the youngest 
of each at the top, thus : 





Bean 


Pea 


Corn 


First Stage 




' 




Second Stage 








Third Stage 








Fourth Stage 








Fifth Stage 

ETC. 









CHAPTER IV 
ROOTS 1 

48. Origin of Roots The primary root originates from 

the lower end of the hypocotyl, as the student learned 
from his own observations on sprouting seeds. The 
branches of the primary root are called secondary roots, 
and the branches of these are known as tertiary roots. 
Those roots which occur on the stem or in other unusual 
places are known as adventitious roots. The roots which 
form so readily on cuttings of willow, southernwood, 
tropseolum, French marigold, geranium (pelargonium), 
tradescantia, and many other plants, when placed in damp 
earth or water, are adventitious. 

49. Aerial Roots. —While the roots of most familiar 
plants grow in the earth and are known as soil-roots, there 
are others which are formed in the air, called aerial roots. 
They serve various purposes : in some tropical air-plants 
(Fig. 13) they serve to fasten the plant to the tree on 
which it establishes itself, as well as to take in water which 
drips from branches and trunks above them, so that these 
plants require no soil and grow in mid-air suspended from 
trees, which serve them merely as supports ; ^ many such 

1 To the plant the root is more important than the stem. The author has, 
however, treated the structure of the latter more fully than that of the root, 
mainly because the tissues are more varied in the stem and a moderate knowl- 
edge of the more complex anatomy of the stem will serve every purpose. 

^ If it can he conveniently managed, the class will find it highly interesting 
and profitable to visit any greenhouse of considerable size, in which the aerial 
roots of orchids and aroids may be examined. 

36 



ROOTS 



57 



air-plants are grown in greenhouses. In suck plants as the 
ivy (Fig. 15) the aerial roots (which are also adventitious) 
hold the plant to the wall or other surface up which it climbs. 

In the Indian corn (Fig. 14) roots are sent out from 
nodes at some dis- 
tance above the 
ground and finally 
descend until they 
enter the ground. 
They serve both to 
anchor the cornstalk 
so as to enable it to 
resist the wind and 
to supply additional 
water to the plant.^ 
They often produce 
no rootlets until they 
reach the ground. 

50. Water-Roots. - 
plants, such as the willow, 
readily adapt their roots to ■. 
live either in earth or in water, 
and some, like the little float- fig. is. 
ing duckweed, regularly pro- 
duce roots which are adapted to live in water .^ 
only. These water-roots often show large and I 

distinct sheaths on the ends of the roots, as, for instance, 
in the so-called water-hyacinth. This plant is especially 
interesting for laboratory cultivation from the fact that 




Aerial 
Roots of au Orchid. 



1 Specimens of tLe lower part of the cornstalk, with ordinary roots and 
aerial roots, should be dried and kept for class study. 



3S 



FOUNDATIONS OF BOTANY 




Fig. 14. — Lower Part of Stem and Roots of Indian Corn, showing Aerial 
Hoots ( " Brace-Roots " ). 

a, c, internodes of the stem ; 6, d, e,/, nodes of various age hearing roots. Most of 
these started as aerial roots, hut all except those from 6 have now reached the earth. 



ROOTS 



39 



it may readily be transferred to moderately damp soil, 
and that tlie whole plant presents curious modifications 
when made to grow in earth instead of water. 

51. Parasitic Roots.^ — The dodder, the mistletoe, and a 
good many other parasites^ live upon nourishment which 
they steal from other plants, called hosts. The parasitic 




Fig. 15. — Aerial Adventitious Eoots of the Ivy. 

roots, or haustoria, form the most intimate connections 
with the interior portions of the stem or the root, as the 
case may be, of the host-plant on which the parasite 
fastens itself. 

In the dodder, as is sho^vn in Fig. 16, it is most inter- 
esting to notice how admirably the seedling parasite is 
adapted to the conditions under which it is to live. Rooted 

1 See Kerner and Oliver's Natural History of Plants, Vol. I, pp. 171-213. 



40 



FOUNDATIONS OF BOTANY 



at first in the ground, it develops a slender, leafless stem, 
which, leaning this way and that, no sooner comes into 




ABC 

Fig. 16. — Dodder, growing upon a Golden-Kod Stem. 

5, seedling dodder plants, growing in earth ; h, stem of host ; r, haustoria or 
parasitic roots of dodder ; I, scale-like leaves. A, magnified section of a por- 
tion of willow stem, showing penetration of haustoria. 

permanent contact with a congenial host than it produces 
haustoria at many points, gives up further growth in its 



ROOTS 



41 



soil-roots, and grows rapidly on the strength of the sup- 
plies of ready-made sap which it obtains from the host. 

52. Forms of Roots The primary root is that which 

proceeds like a downward prolongation directly from the 
lower end of the hypocotyl. In many cases the mature root- 
system of the plant contains one main root much larger 
than any of its branches. This is called a taproot (Fig. 17). 

Such a root, if much thickened, would assume the form 




Fig. 17. — A Taproot. Fig. 18. — l^brous Roots. Fig. 19. — Fascicled Eoots. 

shown in the carrot, parsnip, beet, turnip, salsify, or radish, 
and is called a fleshy root. Some plants produce multiple 
primary roots, that is, a cluster proceeding from the lower 
end of the hypocotyl at the outset. If such roots become 
thickened, like those of the sweet potato and the dahlia 
(Fig. 19), they are known as fascicled roots. 

Roots of grasses, etc., are thread-like, and known as 
fibrous roots (Fig. 18). 

53. General Structure of Roots The structure of the 

very young root can be partially made out by examining 



42 



FOUNDATIONS OF BOTANY 



the entire root with a moderate magnifying power, since 
the whole is sufficiently translucent to allow the interior 
as well as the exterior portion to be studied while the root 
is still alive and growing. 

Place some vigorous cuttings of tradescantia or Zehrina, which 
can usually be obtained of a gardener or florist, in a beaker or jar of 

water.i The iar should 

Q w . _x. p' o be as thin and trans- 

• '^ ■ ^ ' I , . .- parent as possible, and 

it is well to get a flat- 
sided rather than a 
cylindrical one. Leave 
the jar of cuttings in 
a sunny, warm place. 
As soon as roots have 
developed at the nodes 
and reached the length 
of three-quarters of an 
inch or more, arrange 
a microscope in a hori- 
zontal position (see 
Handbook), and exam- 
ine the tip and adjacent 
portion of one of the 
young roots with a 
power of from twelve 
to twentv diameters. 




FJG. 20. — Lengthwise Section (somewhat diagram- 
matic) through Koot-Tip of Indian Corn, x about 130. 



Note : 

(a) The root-cap, 
of . loosely 
attached cells. 

(b) The central 
cylinder. 

1 If the tradescantia or Zehrina cannot be obtained, roots of seedlings of 
oats, wheat, or barley, or of red-clover seedlings raised in a large covered cell 
on a microscope slide, may be used. 



W, root-cap ; i, younger part of cap ; z, dead cells sepa- 
rating from cap ; s, growing point ; o, epidermis ; p', 
intermediate layer between epidermis and central 
cylinder ; p, central cylinder ; d, layer from which 
the root-cap originates. 



ROOTS 43 

(c) The cortical portion, a tubular part enclosing the solid 

central cylinder. 

(d) The root-hairs, which coyer some parts of the outer layer of 

the cortical portion very thickly. Observe particularly 
how far toward the tip of the root the root-hairs extend, 
and where the youngest ones are found. 

Make a drawing to illustrate all the points above suggested 
(a, 5, c, d). Compare your drawing with Fig. 20. Make a careful 
study of longitudinal sections through the centers of the tips of very 
young roots of the hyacinth or the Chinese sacred lily. Sketch 
one section and compare the sketch with Fig. 20. 

Make a study of the roots of any of the common duckweeds, 
growing in nutrient solution in a jar of water under a bell-glass, and 
note the curious root-pockets which here take the place of root-caps. 

54. Details of Root-Structure. — The plan on which the 
young root is built has been outlined in Sect. 53. A few 
further particulars are necessary to an understanding of 
how the root does its work. On examining Fig. 21 the 
cylinders of which the root is made up are easily dis- 
tinguished, and the main constituent parts of each can be 
made out without much trouble. The epidermis-cells are 
seen to be somewhat brick-shaped, many of them provided 
with extensions into root-hairs. Inside the epidermis lie 
several layers of rather globular, thin-walled cells, and 
inside these a boundary layer between the cortical or bark 
portion of the root and the central cylinder. This latter 
region is especially marked by the presence of certain 
groups of cells, shown at w and d and at 5, the two 
former serving as channels for air and water, the latter 
(and w also) giving toughness to the root. 

Roots of shrubs and trees more than a year old will 
be found to have increased in thickness by the process 



44 



FOUNDATIONS OF BOTANY 



described in Sect. 106, and a section may look quite unlike 
the young root-section shown in Fig. 21. 

55. Examination of the Root of a Shrub or Tree. — Cut thin 
transverse sections of large and small roots of any hardwood tree ^ 
and examine them first with a low power of the microscope, as a 
two-inch objective, to get the general disposition of the parts, then 

with a higher power, 
as the half-inch or 
quarter-inch, for de- 
tails. With the low 
power, note: 

(a) The brown 
layer of outer bark. 

(b) The paler layer 
within this. 

(c) The woody cyl- 
inder which forms 
the central portion of 
the root. 

The distinction be- 
tween (b) and (c) is 
more evident when 
the section has been 
exposed to the air for 
a few minutes and 




Fig. 21. —Much Magnified Cross-Section of a 
Very Young Dicotyledonous Eoot. 



h, root-liairs with adhering bits of sand ; e, epidermis ; changed somewhat in 

s, thin-walled, nearly globular cells of bark ; b, hard i tj. • j 

, ' '. ■' * A -i-i ^ ^ 4. color, it is a good 

bast ; c, cambium ; w, wood-cells ; a, ducts. » 

plan to look with the 
low power first at a thick section, viewed as an opaque object, and 
then at a very thin one mounted in water or glycerine, and viewed as 
a transparent object. 

Observe the cut-of£ ends of the ducts, or vessels, which serve as 
passages for air and water to travel through ; these appear as holes in 
the section, and are much more abundant relatively in the young 



1 Young suckers of cherry, apple, 
roots, will afford excellent material. 



etc., which may be pulled up by the 



BOOTS 45 

than in the older and larger portions of the root. Sketch one section 
of each kind. 

Examine with a higher power (100 to 200 diameters), and note the 
ends of the thick-walled wood-cells. Compare these with Fig. 72. 

Notice the many thinner-walled cells composing stripes radiating 
away from the center of the root. These bands are the medullary 
rays, whose mode of origin is shown in Fig. 68. Moisten some of 
the sections with iodine solution,^ and note where the blue color 
shows the presence of starch. Split some portions of the root through 
the middle, cut thin sections from the split surface, and examine with 
the high power some unstained and some stained with iodine. 

Notice the appearance of the wood-cells and the ducts as seen in 
these sections, and compare with Fig. 58.2 

56. Structure and Contents of a Fleshy Root. — In some 
fleshy roots, such as the beet, the morphology of the parts 
is rather puzzling, since they form man}^ layers of tissue 
in a single season, showing on the cross-section of the root 
a series of layers which look a little like the annual rings 
of trees. 

The structure of the turnip, radish, carrot, and parsnip 
is simpler. 

Cut a parsnip across a good deal below the middle, and stand the 
cut end in eosin solution for twenty-four hours. 

Then examine by slicing off successive portions from the upper 
end. Sketch some of the sections thus made. Cut one parsnip 
lengthwise and sketch the section obtained. In what portion of the 
root did the colored liquid rise most readily ? The ring of red marks 
the boundary between the cortical portion and the central cylinder. 
To which does the main bulk of the parsnip belong? Cut thin 
transverse sections from an ink-stained parsnip and notice how the 
medullary rays run out into the cortical portion, and in those sections 

1 If the roots are in their winter condition. 

2 The examination of the minute structure of the root is purposely made 
very hasty, since the detailed study of the structural elements can be made to 
better advantage in the stem. 



46 FOUNDATIONS OF BOTANY 

that show it, find out where the secondary roots arise. If possible, 
peel off the cortical portion from one stained root and leave the cen- 
tral cylinder with the secondary roots attached. Stain one section 
with iodine, and sketch it. Where is the starch of this root mainly 
stored ? 

Test some bits of parsnip for proteids, by boiling them for a 
minute or two with strong nitric acid. 

What kind of plant-food does the taste of cooked parsnips show 
them to contain ? [On no account taste the bits which have been 
boiled in the poisonous nitric acid.] 

57. Storage in Other Roots. — The parsnip is by no 
means a remarkable plant in its capacity for root-storage. 
The roots of the yam and the sweet potato contain a good 
deal of sugar and much more starch than is found in the 
parsnip. Beet-roots contain so much sugar that a large 
part of the sugar supply of Europe and an increasing 
portion of our own supply is obtained from them. Often- 
times the bulk of a fleshy root is exceedingly large as 
compared with that of the parts of the plant above 
ground. 

The South African plant {Harpagophytum^ Chapter 
XXIY) is a good example of this, and another instance 
is that of a plant,^ related to the morning-glory and the 
sweet potato, found in the southeastern United States, 
which has a root of forty or fifty pounds weight. 

Not infrequently roots have a bitter or nauseous taste, 
as in the case of the chicory, the dandelion, and the 
rhubarb, and a good many, like the monkshood, the yellow 
jasmine, and the pinkroot, are poisonous. Can you give 
any reason why the plant may be benefited by the disgust- 
ing taste or poisonous nature of its roots ? 

1 Ipomoea Jalapa. 



ROOTS 



47 



58. Use of the Food stored in Fleshy Roots. — The 

parsnip, beet, carrot, and turnip are biennial plants ; that 
is, they do not produce seed until the second summer or 
fall after they are planted. 

The first season's work consists mainly in producing the 
food which is stored in the roots. To such storage is 
due their characteristic fleshy appear- 
ance. If this root is planted in the 
following spring, it feeds the rapidly 
growing stem which proceeds from the 
bud at its summit, and an abundant 
crop of flowers and seed soon follows ; 
while the root, if examined in late sum- 
mer, will be found to be withered, with 
its store of reserve material quite ex- 
hausted. 

The roots of the rhubarb (Fig. 22), 
the sweet potato, and of a multitude of 
other perennials, or plants which live 
for many years, contain much stored 
plant-food. Many such plants die to 
the ground at the beginning of winter, 
and in spring make a rapid growth from the materials laid 
up in the roots. 

59. Extent of the Root-System. — The total length of 
the roots of ordinary plants is much greater than is usually 
supposed. They are so closely packed in the earth that 
only a few of the roots are seen at a time during the 
process of transplanting, and when a plant is pulled or dug 
up in the ordinary way, a large part of the whole mass of 
roots is broken off and left behind. A few plants have 




Fig. 22. — Fleshy Koots 

of Garden Kliubarb. 

(About one-fifteenth 

natural size.) 



48 FOUNDATIONS OF BOTANY | 

been carefully studied to ascertain the total weight and ; 
length of the roots. Those of winter wheat have been 

found to extend to a depth of seven feet. By weighing j 

the whole root-system of a plant and then weighing a j 

known length of a root of average diameter, the total j 

length of the roots may be estimated. In this way the i 

roots of an oat plant have been calculated to measure j 

about 154 feet ; that is, all the roots, if cut off and strung 1 

together end to end, would reach that distance. i 

Single roots of large trees often extend horizontally to i 

great distances, but it is not often possible readily to trace ': 

the entire depth to which they extend. One of the most \ 

notable examples of an enormously developed root-system j 
is found in the mesquite of the far Southwest and Mexico. 

When this plant grows as a shrub, reaching the height, j 
even in old age, of only two or three feet, it is because the 

water supply in the soil is very scanty. In such cases ; 
the roots extend down to a depth of sixty feet or more, 

until they reach water, and the Mexican farmers in dig- \ 

ging wells follow these roots as guides. Where water is i 

more plenty, the mesquite forms a good-sized tree, with | 

much less remarkably developed roots. i 

60. The Absorbing Surface of Roots. — Such aerial roots 
as are shown in Fig. 13 are usually covered with a spongy 

absorbent layer, by means of which they retain large j 

quantities of the water which trickles down them during | 

rain-storms. This water they afterwards gradually give i 

up to the plant. Most water-roots (not however those of | 

tradescantia) have no special arrangement for absorbing | 
water except through the general surface of their epidermis. 
But some water-roots and most soil-roots take in water 



ROOTS 



49 



mainly through the root-hairs. These are delicate, hair- 
like outgrowths from the epidermis of the root. They 
are, as seen in Fig. 11, thin- walled tubes, of nearly uniform 
diameter, closed at the outer end and opening at the inner 
end into the epidermis-cell from which they 
spring. The relation of each hair to the 
epidermis-cell is still better shown in Fig. 
23, which represents a very young root- 
hair and a considerably older one. 

61. Absorption of Water by Roots. — 
Many experiments on the 
cultivation of corn, wheat, 
oats, beans, peas, and other 
familiar plants in water have 
proved that some plants, at 
any rate, can thrive very 
well on ordinary lake, river, 
or well water, together with 
the food which they absorb 
from the air (Chapter XII). 
Just how much water some 
kinds of plants give off (and 
therefore absorb) per day 
will be discussed when the 
uses of the leaf are studied. 
For the present it is suffi- 
cient to state that even an 
annual plant during its lifetime absorbs through the roots 
very many times its own weight of water. Grasses have been 
known to take in their weight of water in every twenty- 
four hours of warm, dry weather. This absorption takes 




Fig. 23. 
A, a very young root-hair; B, a much 
older one (both greatly magnified). 
f , cells of the epidermis of the root ; 
n, nucleus ; s, watery cell-sap ; p, 
thicker protoplasm, lining the cell- 
wall. 



50 FOUNDATIONS OF BOTANY 

place mainly through, the root-hairs, which the student has 
examined as they occur in the seedling plant, and which 
are found thickly clothing the younger and more rapidly 
growing parts of the roots of mature plants. Some idea 
of their abundance may be gathered from the fact that on 
a rootlet of corn grown in a damp atmosphere, and about 
one-seventeenth of an inch in diameter, 480 root-hairs have 
been counted on each hundredth of an inch of root. The 
walls of the root-hairs are extremely thin, and they have 
no holes or pores visible under even the highest power 
of the microscope, yet the water of the soil penetrates 
very rapidly to the interior of the root-hairs. The 
soil-water brings with it all the substances which it can 
dissolve from the earth about the plant ; and the close- 
ness with which the root-hairs cling to the particles of soil^ 
as shown in Figs. 11 and 21, must cause the water which 
is absorbed to contain more foreign matter than under., 
ground water in general does, particularly since the roots 
give off enough weak acid from their surface to corrode 
the surface of stones which they enfold or cover. 

62. Osmosis. — The process by which two liquids sep- 
arated by membranes pass through the latter and mingle, 
as soil-water does with the liquid contents of root-hairs, is 
called osmosis. 

It is readily demonstrated by experiments with thin 
animal or vegetable membranes. 

EXPERIMENT XV 

Osmosis as shown in an Egg. — Cement to the smaller end of an egg 
a bit of glass tubing about six inches long and about three-sixteenths 
of an inch inside diameter. Sealing-wax or a mixture of equal parts 
of beeswax and resin melted together wiU serve for a cement. 



ROOTS 



51 



Chip away part of the shell from the larger end of the egg, place 
it in a wide-mouthed bottle or a small beaker full of water, as shown 
in Fig. 24, then very cautiously pierce a hole through the upper end 
of the eggshell by pushing a knitting-needle or wire down through 
the glass tube. 

Watch the apparatus for some hours and note any change in the 
contents of the tube.^ Explain. 

The rise of liquid in the tube is evidently due to water making 
its way through the thin membrane which lines the eggshell, 
although this membrane contains no pores visible even under the 
microscope. 

EXPERIMEI^T XVI 

Result of placing Sugar on a Begonia Leaf. — Place a little pow- 
dered sugar on the upper surface of a thick begonia leaf under a small 
bell-glass. Put another por- 
tion of sugar or a bit of paper 
alongside the leaf. Watch for 
several days. Explain results. 
The upper surface of this leaf 
contains no pores, even of 
microscopic size. 

63. Inequality of Os- 
motic Exchange. — The 
nature of the two liquids 
separated by any given 
membrane determines in 
which direction the 
greater flow shall take 
place. 

If one of the liquids is 

Fig. 24. —Egg on Beaker of Water, 

pure water and the other to show osmosis. 




1 Testing the contents of the beaker with nitrate of silver solution will 
then show the presence of more common salt than is found in ordinary water. 
Explain. 



52 FOUNDATIONS OF BOTANY 

is water containing solid substances dissolved in it, the 
greater flow of liquid will be away from the pure water 
into the solution, and the stronger or denser the latter, the 
more unequal will be the flow. This principle is well illus- 
trated by the egg-osmosis experiment. Another important 
principle is that substances which readily crystallize and 
are easily soluble, like salt or sugar, pass rapidly through 
membranes, while jelly-like substances, like white of egg, 
can hardly pass through them at all. 

64. Study of Osmotic Action of Living Protoplasm ; 
Plasmolysis. — The obvious parts of most living and grow- 
ing plant-cells are a cell-wall, which is a skin or enclosure 
made of cellulose, and the living, active cell-contents or 
protoplasm. Every one is familiar with cellulose in vari- 
ous forms, one of the best examples being that afforded by 
clean cotton. It is a tough, white or colorless substance, 
chemically rather inactive. Protoplasm is a substance which 
differs greatly in its appearance and properties under differ- 
ent circumstances. It is of a very complex nature, so far as 
its chemical composition is concerned, belonging to the group 
of proteids and therefore containing not only the elements 
carbon, hydrogen, and oxygen, common to most organic 
substances, but nitrogen in addition. The protoplasm in 
a living cell often consists of several kinds of material ; for 
instance, a rather opaque portion called the nucleus, and a 
more or less liquid portion lining the cell-walls and extend- 
ing inward in strands to the nucleus (Fig. 126). Often, in 
living and active cells, the spaces left between strands and 
lining are filled with a watery liquid called the cell-sap. 

The action of the protoplasm in controlling osmosis is 
well shown by the process known as plasmolysis. 



ROOTS 53 

Put some living threads of pond-scum (^Spirogyra) (Chapter XX) 
into a 4 per cent solution of glycerine in water, a 16 per cent solution 
of cane sugar, or (for quick results) a 2 per cent solution of common 
salt.i Xwj one of these solutions is much denser than the cell-sap 
inside the cells of the pond-scum, and therefore the watery part of 
the cell-contents will be drawn out of the interior of the cell and 
the protoplasmic lining will collapse, receding from the cell-wall. 
The cell-contents are then said to be plasmohjzed. Sketch several 
cells in this condition. Remove the filaments of Spirogyra and 
place them in fresh water. How do they now behave ? Explain. 
Repeat the plasmolyzing operation with another set of cells which 
have first been killed by soaking them for five minutes in a mixture 
of equal quantities of acetic acid, three parts to 1000 of water, and 
chromic acid, seven parts to 1000 of water. The pond-scum threads 
before being transferred from the killing solution into the plas- 
molyzing solution should be rinsed with a little clear water. !N'ote 
how the cells now behave. How is it shown that they have lost 
their power of causing a liquid to be transferred mainly or wholly 
in one direction? Why do frozen or boiled slices of a red beet 
color water in which they are placed, while fresh slices do not? 

65. Osmosis in Root-Hairs. — The soil-water (practically 
identical with ordinary spring or well water) is separated 
from the more or less sugary or mucilaginous sap inside 
of the root-hairs only by their delicate cell-walls, lined 
with a thin layer of protoplasm. This soil- water will pass 
rapidly into the plant, while very little of the sap will 
come out. The selective action, which causes the flow of 
liquid through the root-hairs to be almost wholly inward, 
is due to the living layer of protoplasm (Chapter XII), 
which covers the inner surface of the cell-wall of the root- 
hair. When the student has learned how active a sub- 
stance protoplasm often shows itself to be, he will not be 
astonished to find it behaving almost as though it were 

1 This should be done as a demonstration by the teacher. 



54 FOUNDATIONS OF BOTANY 

possessed of intelligence and will. Plants of two different 
species, both growing in the same soil, usually take from 
it very various amounts or kinds of mineral matter. For 
instance, barley plants in flower and red-clover plants in 
flower contain about the same proportion of mineral mat- 
ter (left as ashes after burning). But the clover contains 
5| times as much lime as the barley, and the latter contains 
about eighteen times as much silica as the clover. This 
difference must be due to the selective action of the proto- 
plasm in the absorbing cells of the roots. Traveling by 
osmotic action from cell to cell, a current of water derived 
from the root-hairs is forced up through the roots and into 
the stem, just as the contents of the egg was forced up 
into the tube shown in Fig. 24. 

66. Root-Pressure. — The force with which the upward- 
flowing current o^ water presses may be estimated by 
attaching a mercury gauge to the root of a tree or the 
stem of a small sapling. This is best done in early spring 
after the thawing of the ground, but before the leaves 
have appeared. The experiment may also be performed 
indoors upon almost any plant with a moderately firm 
stem, through which the water from the soil rises freely. 
A dahlia plant or a tomato plant answers well, though the 
root-pressure from one of these will not be nearly as great 
as that from a larger shrub or a tree growing out of doors. 
In Fig. 25 the apparatus is shown attached to the stem of 
a dahlia. The difference of level of the mercury in the 
bent tube serves to measure the root-pressure. For every 
foot of difference in level there must be a pressure of 
nearly six pounds per square inch on the stump at the 
base of the tube T.^ 

1 See Handbook. 



ROOTS 



56 



A black-birch root tested in this way at the end of 
April has given a root-pressure of thiity-seven pounds to 
the square inch. This would sustain a column of water 
about eighty-six feet high. 

67. Root-Absorption and 
Temperature of Soil. — It 
would not be remarkable if 
the temperature of roots and 
the earth about them had 
something to do with the 
rate at which they absorb 
water, since this absorption 
depends on the living proto- 
plasm of the root-hairs (see 
Sects. 64, 65). An experi- 
ment will serve to throw 
some light on this question. 



EXPERIMENT XYII 




Fig. 25. 



— Apparatus to Measure 
Koot-Pressure. 



T, large tube fastened to the stump of 
the dahlia stem by a rubber tube ; 
rr, rubber stoppers ; t, bent tube 
containing mercury •,11', upper and 
lower level of mercury in T. 



Effect of Temperature on Absorp- 
tion of Water by Roots. — Trans- 
plant a tobacco seedling about four 
inches high into rich earth con- 
tained in a narrow, tall beaker or 
very large test-tube (not less than 
li inch in diameter and six inches high). When the plant has begun 
to grow again freely, in a warm, sunny room, insert a chemical ther- 
mometer into the earth, best by making a hole with a sharp round 
stick, pushed nearly to the bottom of the tube, and then putting the 
thermometer in the place of the stick. Water the plant well, then 
set the tube in a jar of pounded ice which reaches nearly to the 
top of the tube. Note the temperature of the earth just before 
placing it in the ice. Observe whether the leaves of the seedling wilt, 



56 FOUNDATIONS OF BOTANY 

and, if so, at what temperature the wilting begins. Finally, remove 
the tube from the ice and place it in warm water (about 80°). 
Observe the effect and note the temperature at which the plant, 
if wilted, begins to revive. Find an average between the wilting 
temperature and the reviving temperature. For what does this 
average stand? 

68. Movements of Young Roots. — The fact that roots 
usually grow downward is so familiar that we do not 
generally think of it as a thing that needs discussion or 
explanation. Since they are pretty flexible, it may seem 
as though young and slender roots merely hung down 
by their own weight, like so many bits of wet cotton 
twine. But a very little experimenting will answer the 
question whether this is really the case. 

EXPERIMENT XVIII 

Do all Parts of the Root of the Windsor Bean Seedling bend down- 
ward alike? — Fasten some sprouting Windsor beans with roots 
about an inch in length to the edges of a disk of pine wood or 
other soft wood in a soup-plate nearly full of water and cover them 
with a low bell-jar. Pins run through the cotyledons, as in Fig. 26, 
will hold the beans in place. When the roots have begun to point 
downward strongly, turn most of the beans upside down and pin 
them in the reversed position. If you choose, after a few days 
reverse them again. Make sketches of the various forms that the 
roots assume and discuss these. 

EXPERIMENT XIX 

Does the Windsor Bean Root-Tip press downward with a Force 
greater than its Own Weight ? — Arrange a sprouted bean as shown 
in Fig. 26, selecting one that has a root about twice as long as the 
diameter of the bean and that has grown out horizontally, having 
been sprouted on a sheet of wet blotting paper. The bean is pinned 



ROOTS 



57 




Fig. 26. —A Sprouting Windsor Bean pushing its 
Eoot-Tip into Mercury. 

s, seed ; r, root ; w, layer of water ; ??;, mercury. 



to a cork that is fastened with beeswax and resin mixture to the 
side of a little trough or pan of glass or glazed earthenware. The 
pan is filled half an inch or more with mercury, and on top of 
the mercury is a layer 
of water. The whole 
is closely covered by 
a large tumbler or a 
bell-glass. Allow the 
aj)paratus to stand un- 
til the root has forced 
its way down into the 
mercury. Then run a 
slender needle into the 
root where it enters 
the mercury (to mark 
the exact level), withdraw the root, and measui-e the length of 
the part submerged in mercury. To see whether this part would 
have stayed under by virtue of its own ;^eight, cut it off- and lay 
it on the mercury. Push it under with a pair of steel forceps and 
then let go of it. What does it do ? 

69. Discussion of Exp. XIX. — By comparing the weights 
of equal bulks of mercury and Windsor bean roots, it is 
found that the mercury is about fourteen times as heavy 
as the substance of the roots. Evidently, then, the sub- 
merged part of the root must have been held under by 
a force about fourteen times its own weight. Making fine 
equidistant cross-marks with ink along the upper and the 
lower surface of a root that is about to bend downward at 
the tip, readily shows that those of the upper series soon 
come to be farther apart, — in other words, that the root is 
forced to hend downward hy the more rapid growth of its 
upper as compared with its under surface. 

70. Geotropism. — The property which plants or their 
organs manifest, of assuming a definite direction with 



58 FOUNDATIONS OF BOTANY 

reference to gravity,^ is called geotropism. When, as in 
the case of the primary root, the effect of gravity is to 
make the part if unobstructed turn or move downward, 
we say that the geotropism is positive. If the tendency is 
to produce upward movement, we say that the geotropism 
is negative; if horizontal movement, that it is lateral. It 
was stated in the preceding section that the direct cause 
of the downward extension of roots is unequal growth. 
We might easily suppose that this unequal growth is not 
due to gravity, but to some other cause. To test this sup- 
position, the simplest plan (if it could be carried out) would 
be to remove the plants studied to some distant region 
where gravity does not exist. This of course cannot be 

done, but we can easily turn a 
young seedling over and over 
so that gravity will act on it 
now in one direction, now in 
another, and so leave no more 
impression than if it did not act 
at all (Exp. XX). Or we can 
whirl a plant so fast that not 
only is gravity done away with, 

FIG. 27.-sprouting Peas, on the Disk ^ut another forcc is introduced 
of a rapidly Whirling ciinostat. in its placc. If a Vertical wheel, 

The youngest portions of the roots ;[i]^g ^ carriage wliecl, wcrc pro- 
all point directly away from the _ ° -^ 

axis about which they were re- vidcd with a fcW loOSCly fitting 

volved. • • 1. iU 1 

iron rings strung on the spokes, 
when the wheel was revolved rapidly the rings would all 
fly out to the rim of the wheel. So in Fig. 27 it will be 



1 Gravity means the pull which the earth exerts upon all objects on or 
near its surface. 




ROOTS 69 

noticed that the growing tips of the roots of the sprouting 
peas point almost directly outward from the center of the 
disk on which the seedlings are fastened. Explain the differ- 
ence between this result and that obtained in Exp. XX. 

EXPERIMENT XX 

How do Primary Roots point when uninfluenced by Gravity ? Pin 
some soaked Windsor beans to a large flat cork, cover them with 
thoroughly moistened chopped peat-moss, and cover this with a thin 
glass crystallizing dish. Set the cork on edge. Prepare another 
cork in the same way, attach it to a clinostat, and keep it slowly 
revolving in a vertical position for from three to five days. Com- 
pare the directions taken by the I'oots on the stationary and on the 
revolving cork.^ 

71. Direction taken by Secondary Roots. — As the stu- 
dent has already noticed in the seedlings which he has 
studied, the branches of the primary root usually make a 
considerable angle with it (Fig. 2). Often they run out 
for long distances almost horizontally. This is especially 
common in the roots of forest trees, above all in cone- 
bearing trees, such as pines and hemlocks. This horizon- 
tal or nearly horizontal position of large secondary roots 
is the most advantageous arrangement to make them use- 
ful in staying or guying the stem above, to j^revent it from 
being blown over by the wind. 

72. Fitness of the Root for its Position and Work. — The 
distribution of material in the woody roots of trees and 
shrubs and their behavior in the soil show many adapta- 
tions to the conditions by which the roots are surrounded. 

1 See Ganong's Teaching Botanist, pp. 182-186, for complete directions. 
The brief statement above given is abstracted from that of Professor Ganong. 



60 



FOUNDATIONS OF BOTANY 



The growing tip of the root, as it pushes its way through 
the soil, is exposed to bruises ; but these are largely warded 
off by the root-cap. The tip also shows a remarkable 
sensitiveness to contact with hard objects, so that when 
touched by one it swerves aside and thus finds its way 
downward by the easiest path. Roots with an unequal 
water supply on either side grow toward the moister soil. 
Roots are very tough, because they need to resist strong 







'^^"^mc^. 



~r^. 



Fig. 28. — Roots of a Western Hemlock exposed by having most of the Leaf -Mould 
about them burned away by Forest Fires. 



pulls, but not as stiff as stems and branches of the same 
size, because they do not need to withstand sidewise pres- 
sure, acting from one side only. The corky layer which 
covers the outsides of roots is remarkable for its power 
of preventing evaporation. It must be of use in retaining 
in the root the moisture which otherwise might be lost 
on its way from the deeper rootlets (which are buried in 
damp soil), through the upper portions of the root-system, 
about which the soil is often very dry. 



I 



ROOTS 61 

73. Propagation by Means of Roots. — Some familiar 
plants, such as rose bushes, are usually grown from roots 
or root-cuttings. 

Bury a sweet potato or a dahlia root in damp sand, and watcii 
the development of sprouts from adventitious buds. One sweet 
potato will produce several such crops of sprouts, and every sprout 
may be made to grow into a new plant. It is in this way that the 
crop is started wherever the sweet potato is grown for the market. 

74. Tabular Review of Experiments. 

[Continue the table begun at end of Chapter III.] 

75. Review Summary of Roots. 

Kinds of roots as regards origin < 

f 

Kinds as regards medium in which they grow . -^ 

Structure of root of a tree. 

r materials. 
Storage in roots ^ location. 

louses. 

f apparatus. 

Absorption of water by roots J 

I proofs. 

I causes. 

r nature. 
Movements of roots J causes. 

louses. 



CHAPTER y 
STEMS 

76. What the Stem is The work of taking in the raw 

materials which the plant makes into its own food is done 
mainly by the roots and the leaves. These raw materials 
are taken from earth, from water, and from the air (see 
Chapter XI). The stem is that part or organ of the plant 
which serves to bring roots and leaves into communication 
with each other. In most flowering plants the stem also 
serves the important purpose of lifting the leaves up into 
the sunlight, where alone they best can do their special 
work. 

The student has already, in Chapter III, learned some- 
thing of the development of the stem and the seedling ; 
he has now to study the external appearance and internal 
structure of the mature stem. Much in regard to this 
structure can conveniently be learned from the examina- 
tion of twigs and branches of our common forest trees in 
their winter condition. 

77. The Horse-Chestnut Twig.^ — Procure a twig of horse-chest- 
nut eighteen inches or more in length. . Make a careful sketch of it, 
trying to bring out the following points : 

(1) The general character of the bark. 

1 Where the huckeye is more readily obtained it will do very well. Hick- 
ory twigs answer the same purpose, and the latter is a more typical form, 
having alternate buds. The magnolia or the tulip tree will do. The student 
should (sooner or later) examine at least one opposite- and one alternate-leaved 
twig. 

62 



STEMS 



63 



(2) The large horseshoe-shaped scars and the number and posi- 
tion of the dots on these scars. Compare a scar with the base of a 
leaf-stalk furnished by the teacher. 

(3) The ring of narrow scars around the stem in one or more 
places,^ and the different appearance of the bark above and below 
such a ring. Compare these scars with those left after removing the 
scales of a terminal bud and then see Fig. 29, h sc. ^ 

(4) The buds at the upper margin of each leaf- ^ 
scar and the strong terminal bud at the end of the m 
twig. 

(5) The flower-bud scar, a concave impression, 
to be found in the angle produced by the forking 
of two twigs, which form, with the branch from 
which they spring, a Y-shaped figure (see Fig. 36). 

(6) (On a branch larger than the twig handed 
round for individual study) the place of origin of 
the twigs on the branch ; — make a separate sketch 
of this. 

The portion of stem which originally bore any 
pair of leaves is called a node, and the portions of 
stem between nodes are called internodes. 

Describe briefly in writing alongside the sketches 
any observed facts which the drawings do not show. 

If your twig was a crooked, rough-barked, and 
slow-growing one, exchange it for a smooth, vig- 

A + ^-u A'ff r^ -J Fig. 29. -A quickly 

orous one, and note the differences. Or if you grown Twig of 
sketched a quickly grown shoot, exchange for one Ciierry, with Lat- 
of the other kind. ^^^^ ^"^ Terminal 

Buds in October. 
Answer the following questions : 



b sc 



did 



your twig grow 



(a) How many inches 
dmdng the last summer? 

How many in the summer before ? 

How do you know ? 

How many years old is the whole twig given you ? 

(&) How were the leaves arranged on the twig ? 

1 A very vigorous shoot may not show any such ring. 



6 sc, bud-scale scars. 
All above these 
scars is the growth, 
of the spring and 
summer of the 
same year. 



64 FOUNDATIONS OJ^ BOTANY 

How many leaves were there ? 
Were they all of the same size ? 

(c) What has the mode of branching to do with the arrangement 
of the leaves ? with the flower-bud scars ? 

(d) The dots on the leaf-scars mark the position of the bundles 
of ducts and wood-cells which run from the wood of the branch 
through the leaf-stalk up into the leaf. 

78. Twig of Beech. — Sketch a vigorous yoiing twig of beech (or 
of hickory, magnolia, tulip tree) in its winter condition, noting par- 
ticularly the respects in which it differs from the horse-chestnut. 
Describe in writing any facts not shown in the sketch. Notice that 
the buds are not opposite, nor is the next one above any given bud 
found directly above it, but part way round the stem from the posi- 
tion of the first one. Ascertain, by studying several twigs and 
counting around, which bud is above the first and how many turns 
round the stem are made in passing from the first to the one directly 
above it. 

Observe with especial care the difference between the beech and 
the horse-chestnut in mode of branching, as shown in a large branch 
provided for the study of this feature. 

79. Relation of Leaf -Arrangement to Branching.^ — This 
difference, referred to in Sect. 78, depends on the fact that 
the leaves of the horse-chestnut were arranged in pairs, on 
opposite sides of the stem, while those of the beech were 
not in pairs. Since the buds are found at the upper edges 
of the leaf-scars, and since most of the buds of the horse- 
chestnut and the beech are leaf-buds and destined to form 
branches, the mode of branching and ultimately the form 

1 The teacher in theJEastern and Middle States will do well to make constant 
use, in the study of branches and buds, of Miss Newell's Outlines of Lessons 
in Botany, Part I. The student can observe for himself, with a little guid- 
ance from the teacher, most of the points which Miss Newell suggests. If the 
supply of material is abundant, the twigs employed in the lessons above 
described need not be used further, but if material is scanty, the study of buds 
may at once be taken up, (See also Bailey's Lessons with Plants, Part I.) 



STEMS 



65 



of the tree must depend largely on the arrangement of 

leaves along the stem. 

80. Opposite Branching In trees the leaves and buds 

of which are opposite, the tendency will be to form twigs 

in four rows about at right angles 

to each other along the sides of 

the branch, as shown in Fig. 30. 

This arrangement will not usu- 
ally be perfectly carried out, since 

some of the buds may never grow, 
or some may 
grow much 
faster than 
others and so 
make the plan 
of branching less 
evident than it 
would be if all 
grew alike. 

81. Alternate 
Branching. — In 

trees like the beech the twigs will be 
found to be arranged in a more or less 
regular spiral line about the branch. 
This, which is known as the alternate 
arrangement (Fig. 31), is more com- 
monly met with in trees and shrubs 
than the opposite arrangement. It ad- 
mits of many varieties, since the spiral 

may wind more or less rapidly round the stem. In the 

apple, pear, cherry, poplar, oak, and walnut, one passes 





Fig. 30. — Opposite Branching 

in a very Young Sapling 

of Ash. 



Fig. 31. — Alternate 
Branching in a very 
Young Apple Tree. 



FOUNDATIONS OF BOTANY 




Fig. 32.- 



Excurreiit Trunks of Big Trees 
(Seqiwias). 



over five spaces before 
coming to a leaf which 
is over the first, and in 
doing this it is necessary 
to make two complete 
turns round the stem 
(Fig. 105). 

82. Growth of the Ter- 
minal Bud. — In some 
trees the terminal bud 
from the very outset 
keeps the leading place, 
and the result of this 
mode of growth is to 
produce a slender, up- 
right tree, with an excur- 
rent trunk like that of 
Fig. 32. 

In such trees as the 
apple and many oaks the 
terminal bud has no pre- 
eminence over others, and 
the form of the tree is 
round-topped and spread- 
ing, deliquescent like that 
in Fig. 33. 

Most of the larger for- 
est trees are intermediate 
between these extremes. 

Branches get their 
characteristics to a 



STEMS 



67 




Fig. 33.— An American Elm, witli Deliquescent Trunk. 

considerable degree from the relative importance of their 
terminal buds. If these are mainly flower-buds, as is the case 
in the horse-chestnut and some magnolias (Figs. 35, 36), 



68 EOUNDATIOIN^S OF BOTANY 

the tree is characterized by frequent forking, and has 
no long horizontal branches. 

If the terminal bud keeps the lead of the lateral ones, 
but the latter" are numerous and most of them grow into 
slender twigs, the delicate spray of the elm and many 
birches is produced (Fig. 37). 

The general effect of the branching depends much upon 
the angle which each branch or twig forms with that one 
from which it springs. The angle may be quite acute, as 
in the birch ; or more nearly a right angle, as in the ash 
(Fig. 30). The inclination of lateral branches is due to 
geotropism, just as is that of the branches of primary roots. 
The vertically upward direction of the shoot which grows 
from the terminal bud is also due to geotropism. 

This is really only a brief way of saying that the grow- 
ing tip of the main stem of the tree or of any branch is 
made to take and keep its proper direction, whether verti- 
cally upward or at whatever angle is desirable for the tree, 
by the steering action of gravity. After growth has ceased 
this steering action can no longer be exerted, and so a tree 
that has been bent over (as, for instance, by a heavy load 
of snow) cannot right itself, imless it is elastic enough to 
spring back when the load is removed. The tip of the 
trunk and of each branch can grow and thus become 
vertical, but the old wood cannot do so. 

83. Thorns as Branches. — In many trees some branches 
show a tendency to remain dwarfish and incompletely 
developed. Such imperfect branches forming thorns are 
familiar in wild crab-apple trees and in the pear trees 
which occur in old pastures in the Northeastern States. In 
the honey locust very formidable branching spines spring 



STEMS 



69 



from adventitious or dormant buds on the trunk or limbs. 
Such spines sometimes show their true nature as branches 
by bearing leaves (Fig. 34). 

84. Indefinite Annual Growth. — In most of the forest 
trees, and in the larger shrubs, the wood of young branches 
is matured and fully 
developed during the 
summer. Protected 
buds are formed on 
the twigs of these 
branches to their very 
tips. In other shrubs 
— for example, in the 
sumac, the raspberry, 
and blackberry — the 
shoots continue to 
grow until their soft 
and immature tips are 
killed by the frost. 

Such a mode of growth is called indefinite 
annual groivtli^ to distinguish it from the 
definite annual growth of most trees. 

85. Trees, Shrubs, and Herbs. — Plants 
of the largest size with a main trunk of a 
woody structure are called trees. Shrubs 
differ from trees in their smaller size, and 

generally in having several stems which proceed from the 
ground or near it or in having much-forked stems. The 
witch-hazel, the dogwoods, and the alders, for instance, 
are most of them classed as shrubs for this reason, though 
in height some of them equal the smaller trees. Some of 




Fig. 34. — Leaf -Bearing Spine 
of Honey Locust. 




70 



rOUNDATIONS OF BOTANY 



the smallest shrubby plants, like the dwarf blueberry, the 
wintergreen, and the trailing arbutus, are only a few inches 




Fig. 35. — Tip of a Branch of Magnolia, illustrating Forking due to 
Terminal Flower-Buds. 

A, oldest flower-bud scar ; B, C, D, scars of successive seasons after A; L, leaf- 
buds ; F, flower-buds. 



in height, but are ranked as shrubs because their woody 
stems do not die quite to the ground in winter. 

Herbs are plants whose stems above ground die every 
winter. 



STEMS 



Tl 



86. Annual, Biennial, and Perennial Plants. — Annual 

plants are those which live but one year, biennials those 
which live two years 
or nearly so. 

Some annual plants 
may be made to live 
over winter, flower- 
ing in their second 
summer. This is true 
of winter wheat and 
rye among cultivated 
plants. 

Perennial plants live for a series of 
years. Many kinds of trees last for 
centuries. The Californian giant redwoods, or Sequoias 
(Fig. 32), which reach a height of over 300 feet under 
favorable circumstances, live nearly 2000 years ; and some 




Fig. 36. —A Portion of 

the Branch of Fig. 35. 

(Natural size.) 



/ ' '!< lillJ 




Fig. 37. —Twigs and 

Branches of the 

Birch. 



monstrous cypress trees found in Mexico were thought by 
Professor Asa Gray to be from 4000 to 5000 years old. 



72 



rOUNDATIONS OF BOTANY 



87. Stemless Plants. — As will be shown later (Chap- 
ter XXX), plants live subject to a very fierce competition 
among themselves and exposed to almost constant attacks 
from animals. 

While plants with long stems find it to their advantage 
to reach up as far as possible into the sunlight, the cinque- 
foil, the white clover, 
the dandelion, some 
spurges, the knot- 




grass, 



and hundreds 



of other kinds of 
plants have found 
safety in hugging 
the ground. 

Any plant which 
can grow in safety 
under the very feet 
of grazing animals 
will be especially 
likely to make its 
way in the world, 
since there are many 
places where it can 
flourish while ordi- 
nary plants would be destroyed. The bitter, stemless 
dandelion, which is almost uneatable for most animals, 
unless cooked, which lies too near the earth to be fed 
upon by grazing animals, and which bears being trodden 
on with impunity, is a type of a large class of hardy weeds. 
The so-called stemless plants, like the dandelion (Fig. 38), 
and some violets, are not really stemless at all, but send 



Fig. 38. — The Dandelion ; a so-called 
• Stemless Plant. 



STEMS 



73 







out their leaves and flowers from a very short stem, which 
hardly rises above the surface of the ground. 

88. Climbing and Twining Sterns.^ — Since it is essen- 
tial to the health and rapid growth of most plants that 
they should have free access 
to the sun and air, it is not 
strange that many should 
resort to special devices for 
lifting themselves above 
their neighbors. In tropi- 
cal forests, where the dark- 
ness of the shade anywhere 
beneath the tree-tops is so 
great that few flowering 
plants can thrive in it, the 
climbing plants or lianas 
often run like great cables 
for hundreds of feet before 
they can emerge into the sun- 
shine above. In temperate 
climates no such remarkable 
climbers are found, but many 
plants raise themselves for 
considerable distances. The 
principal means to which they resort for this purpose are : 

(1) Producing roots at many points along the stem 
above ground and climbing on suitable objects by means 
of these, as in the English ivy (Fig. 15). 

(2) Laying hold of objects by means of tendrils or 
twining branches or leaf-stalks, as shown in Figs. 40, 41. 

1 See Kerner and Oliver's Natural History of Plants, Vol. I, p. 669. 




Fia. 39. —Lianas strangling a Palm. 



74 



FOUNDATIONS OE BOTANY 



(3) Twining about any slender upright support, as 
shown in Fig. 42. 

89. Tendril-Climbers. — The plants which climb by 
means of tendrils are important subjects for study, but 
they cannot usually be managed very well in the school- 
room. Continued observation soon shows that the tips of 

tendrils sweep slowly about in 
the air until they come in contact 
with some object about which 
they can coil themselves. After 
the tendril has taken a few turns 
about its support, the free part of 
the tendril coils into a spiral and 
thus draws the whole stem toward 
the point of attachment, as shown 
in Fig. 40. Some tendrils are 
modified leaves or stipules, as 
shown in Fig. 104 ; others are 
modified stems. 

90. Twiners. — Only a few of 
the upper internodes of the stem 
of a twiner are concerned in pro- 
ducing the movements of the tip 
of the stem. This is kept revolving in an elliptical o?,' 
circular path until it encounters some roughish and not too 
stout object, about which it then proceeds to coil itself. 

The movements of the younger internodes of the stems 
of twiners are among the most extensive of all the move- 
ments made by plants. A hop-vine which has climbed to 
the top of its stake may sweep its tip continually around 
the circumference of a circle two feet in diameter, and the 




Fig 40. 



-Coiling of a Tendril 
of Bryony. 



STEMS 



75 



common wax-plant of the greenhouses sometimes describes 
a five-foot circle, the tip moving at the rate of thirty-two 
inches per hour.^ This circular motion results from 
some cause not yet fully understood by botanists .^ 

The direction in Avhich twiners coil about a supporting 
object is almost always the same for each species of plant, 
but not the same for all 
species. In the hop it is as 




Fig. 41. — Coiling of Petiole of Dwarf 
Tropseolum. 



Fig. 42. — Twining Stem of Hop. 



shown in Fig. 42. Is it the same as in the bean ? in the 
morning-glory ? 

91. Underground Stems. — Stems which lie mainly or 
wholly underground are of frequent occurrence and of 
many kinds. 

In the simplest form of rootstocJc (Fig. 43), such as is 

1 See article on Climbing Plants, by Dr. W. J. Beal, in the American 
Naturalist, Vol. IV, pp. 405-415. 

2 See Strasburger, Noll, Schenk, and Schimper, Text-Book, ^^i^. 258-262; 
also Vines, Students' Text-Book of Botany, London and New York, 1894, 
pp. 759, 760. 



76 



FOUNDATIONS OF BOTANY 



.ts.W,ft/\«% 



found in some mints and in many grasses and sedges, the 
real nature of the creeping underground stem is shown by 

the presence upon its sur- 
face of many scales, which 
are reduced leaves. Root- 
stocks of this sort often 
extend horizontally for 
long distances in the case 
of grasses like the sea rye 
grass (Plate I), which roots 
itself firmly and thrives in 
shifting sand-dunes. In 
the stouter rootstocks, like 
that of the iris (Fig. 44) 
and the Caladium (Fig. 
45), this stem-like charac- 
ter is less evident. The 
potato is an excellent ex- 
ample of the short and 
much-thickened under- 
ground stem known as a 
tuber. 

It may be seen from Fig. 

46 that the potatoes are 

none of them borne on true 

roots, but only on subter- 

ranean 

branches, 

which are 

stou ter 

The " eyes " 





Fig. 43. — Rootstock of Cotton-Grass (Eriophorum). 

and more cylindrical than most of the roots. 



STEMS 



77 




which they bear are rudi- 
mentary leaves and buds. 

Bulbs, whether coated 
like those of the onion or 
the hyacinth (Fig. 47), or 
scaly like those of the 
lily, are merely very short 
and stout underground 
stems, covered with closely 
crowded scales or layers 
which represent leaves or 
the bases of leaves (Fig. 48). 

The variously modified 
forms of underground 
stems just discussed, illus- 



Fig. 44. — Koots, Rootstocks, and 
Leaves of Iris. 

trate in a marked way the storage 
of nourishment during the winter 
(or the rainless season, as the case 
may be) to secure rapid growth dur- 
incr the active season. It is inter- 
esting to notice that nearly all of 
the early-flowering herbs in temper- 
ate climates, like the crocus, the 
snowdrop, the spring-beauty, the 




Fig. 45. — Rootstock of Cala- 
dium (Colocasla). 

b, terminal bud ; b', buds ar- 
ranged in circles where bases 
of leaves were attached ; s, 
scars left by sheathing bases 
of leaves. 



78 



FOUNDATIONS OF BOTANY 



tulip, and the skunk-cabbage, owe their early-blooming 
habit to richly stored underground stems of some kind, 
or to thick, fleshy roots. 

92. Condensed Stems. — The plants of desert regions 
require, above all, protection from the extreme dryness of 
the surrounding air, and, usually, from the excessive heat 

of the sun. Ac- 
cordingly, many 
desert plants are 
found quite desti- 
tute of ordinary 
foliage, exposing 
to the air only a 
small surface. In 
the melon-cactuses 
(Fig. 49) the stem 
appears reduced 
to the shape in 
which the least 
possible surface is 
presented by a 
plant of given 
bulk, — that is, in 
a globular form. Other cactuses are more or less cylindri- 
cal or prismatic, while still others consist of flattened 
joints ; but all agree in offering much less area to the sun 
and air than is exposed by an ordinary leafy plant. 

93. Leaf -Like Stems. — The flattened stems of some kinds 
of cactus (especially the common, showy Phyllocactus) are 
sufliciently like fleshy leaves, with their dark green color 
and imitation of a midrib, to pass for leaves. There are, 




Fig. 46. — Part of a Potato Plant. 

The dark tuber in the middle is the one from which 

the plant has grown. 



STEMS 



79 




Fig. 47. —Bulb of Hyaciuth. 
(Exterior view and split lengthwise.) 



however, a good many cases in which the stem takes on 

a more strikingly leaf-like form. The common asparagus 

sends up in spring shoots 
that bear large scales which 
are really reduced leaves. 
Later in the season, what 
seem like thread-like leaves 
cover the much-branched 
mature plant, but these 
green threads ^'/z/ 

are actually mi- 
nute branches, 
which perform 
the work of 

leaves (Fig. 50). The familiar greenhouse 

climber, wrongly known as smilax (properly 

called Myrsiphyllum)^ bears a profusion of 

what appear to be delicate green leaves 

(Fig. 51). Close study, however, shows that 

these are really short, flattened branches, 

and that each little branch springs from 

the axil of a true leaf, Z, in the form 

of a minute scale. Sometimes a flower 

and a leaf-like branch spring from the 

axil of the same scale. 

Branches which, like those of Myrsi- 

phyllum^ so closely resemble leaves as to 

be almost indistinguishable from them are 

called cladophylls. 

94. Modifiability of the Stem. — The stem may, as in the 

tallest trees, in the great lianas of South American forests. 




sea 



Fig. 48. — Longitu- 
dinal Section of 
an Onion Leaf. 

sea, thickened base 
of leaf, forming a 
bulb-scale; s,thin 
sheath of leaf ; hi, 
blade of the leaf ; 
int, hollow inte- 
rior of blade. 



80 



FOUNDATIONS OF BOTANY 



I , 








Pig, 49. —A Melon-Cactus. 







Fig. 50. —A Spray of a Common Asparagus (not the edible species). 



STEMS 



81 



or the rattan of Indian jungles, reach a length of many 
hundred feet. On the other hand, in such "stemless" 
plants as the primrose and the dandelion, the stem may be 
reduced to a fraction of an inch in length. It may take 




Fig. 51. — Stem of " Smilax" (Myrsiphyllum). 

I, scale-like leaves ; cl, cladophyU, or leaf-like branch, growing in the axil of the 

leaf ; ped, flower-stalk, growing in the axil of a leaf. 



on apparently root-like forms, as in many grasses and 
sedges, or become thickened by underground deposits of 
starch and other plant-food, as in the iris, the potato, and 
the crocus. Condensed forms of stem may exist above 
ground, or, on the other hand, branches may be flat and 



82 



FOUNDATIONS OF BOTANY 



thin enough closely to imitate leaves. In short, the stem 
manifests great readiness in adapting itself to the most 
varied conditions of existence. 



95. Review Summary of Stems. ^ 

Kinds of branching due to leaf arrangement 



Kinds of tree-trunk due to greater or less predominance 
of terminal bud 



Classes of plants based on amount of woody stem 
Classes of plants based on duration of life . . , 



Various modes of climbing 



Kinds of underground stem 



Condensed stems above ground 



Leaf-like stems 



1 Where it is possible to do so, make sketches ; where this is not possible, 
give examples of plants to illustrate the various kinds or classes of plants in 
the summary. 



CHAPTER VI 



STRUCTURE OF THE STEM 



STEM OF mo:n^ocotyledonous plants 



96. Gross Structure. — Refer back to the sketches of the corn 
seedling, to recall something of the early history of the corn-stem. 
Study the external appearance of a piece of corn-stem or bamboo 
two feet or liiore in length. 'Note the character of the outer surface. 
Sketch the whole piece and label the enlarged nodes and the nearly 
cylindrical internodes. Cut across a corn-stem and examine the cut sur- 
face with the magnifying glass. 
Make some sections as thin as 
they can be cut and examine 
with the magnifying glass 
(holding them up to the light) 
or with a dissecting microscope. 
Note the firm rind, composed 
of the epidermis and underlying 
tissue, the large mass of pith 
composing the main bulk of the 
stem, and the many little harder 
and more opaque spots, which 
are the cut-off ends of the 
woody threads known Sisjihro- 
vascular bundles (Fig. 52). 

Split a portion of the stem 
lengthwise into thin translucent 
slices and notice whether the 
bundles seem to run straight up and down its length; sketch the 
entire section x 2. Every fibro-vascular bundle of the stem passes out- 
ward through some node in order to connect with some fibro-vascular 

83 




Fig. 52. — Diagrammatic Cross-Section 

of Stem of Indian Corn. 

cv, fibro-vascular Tjundles ; gc, pithy material 

between bundles. 



84 



FOUNDATIONS OE BOTANY 



bundle of a leaf. This fact being known to the student would lead 
him to expect to find the bundles bending out of a vertical position 
more at the nodes than elsewhere. Can this be seen in the stem 
examined ? 

Observe the enlargement and thickening at the nodes, and split 
one of these lengthwise to show the tissue within it. 

Compare with the corn-stem a piece of palmetto and a piece of 
cat-brier {Smilax rotundifoUa, S. Mspida, etc.), and notice the simi- 
larity of structure, except for the fact that the tissue in the palmetto 
and the cat-brier which answers to the pith of the corn-stem is much 
darker colored and harder than corn-stem pith. Compare also a piece 
of rattan and of bamboo. 

97. Minute Structure. — Cut a thin cross-section of the corn-stem, 
examine with a low power of the microscope, and note : 

(a) The rind (not true bark), composed largely of hard, thick- 
walled dead cells, known as sclerenchyma fibers. 

(5) The fibro-vascular bundles. Where are they most abundant ? 
least abundant ? 

(c) The pith, occupying the intervals between the fibro-vascular 
bundles. 

Study the bundles in various portions of the section and notice 
particularly whether some are more porous than others. Explain. 
Sketch some of the outer and some of the 
inner ones. 

A more complicated kind of monocoty- 
ledonous stem-structure can be studied to 
advantage in the surgeons' splints cut from 
yucca-stems and sold by dealers in surgical 
supplies. 




98. Mechanical Function of the 
Manner of Distribution of Material 
in Monocotyledonous Stems. — The 

well-known strength and lightness of 
the straw of our smaller grains and of rods of cane or 
bamboo are due to their form. It can readily be shown 



Fig. 53. — Diagrammatic 
Cross-Section of Stem of 
Bulrush (Scirpus), a 
Hollow Cylinder with 
Strengthening Fibers. 



STRUCTURE 0¥ THE STEM 



85 



by experiment that an iron or steel tube of moderate thick- 
ness, like a piece of gas-pipe, or of bicycle-tubing, is much 
stiffer than a solid rod of the same weight per foot. The 
oat straw, the stems of bulrushes (Fig. 53), the cane (of 
our southern canebrakes), and the bamboo are hollow 
cylinders ; the 
cornstalk is a 
solid cylinder, 
but filled with a 
very light pith. 
The flinty outer 
layer of the 
stalk, together 
with the closely 
packed scleren- 
chyma fibers of 
the outer rind 
and the frequent 
fibro-vascular 
bundles just 
within this, are 
arranged in the 
best way to se- 
cure stiffness. 
In a general 
way, then, we may say that the pith, the bundles, and the 
sclerenchymatous rind are what they are and where they 
are to serve important mechanical purposes. But they 
have other uses fully as important (Fig. 78). 

99. Growth of Monocotyledonous Stems in Thickness. — 
In most woody monocotyledonous stems, for a reason 




Fig. 54. — Group of Date-Palms. 



86 FOUNDATIONS OF BOTANY 

which will be explained later in this chapter, the increase 
in thickness is strictly limited. Such stems, therefore, as 
in many palms (Fig. 54) and in rattans, are less conical 
and more cylindrical than the trunks of ordinary trees 
and are also more slender in proportion to their height. 



STEM OF DICOTYLEDONOUS PLANTS 

100. Gross Structure of an Annual Dicotyledonous Stem. — Study 
the external appearance of. a piece of sunflower-stem several inches 
long. If it shows distinct nodes, sketch it. Examine the cross- 
section and sketch it as seen with the magnifying glass or the dissect- 
ing microscope. After your sketch is finished, compare it with Fig. 55, 
which probably shows more details than your drawing, and label 
the parts shown as they are labeled in that figure. Split a short 
piece of the stem lengthwise through the center and study the split 
surface with the magnifying glass. Take a sharp knife or a scalpel 
and carefully slice and then scrape away the bark until you come to 
the outer surface of a bundle. 

Examine a vegetable sponge {Luffa), sold by druggists, and notice 
that it is simply a network of fibro-vascular bundles. It is the skele- 
ton of a tropical seed-vessel or fruit, very much like that of the wild 
cucumber, common in the Central States, but a great deal larger. 

The different layers of the bark cannot all be well recognized in the 
examination of a single kind of stem. Examine (a) the cork which 
constitutes the outer layers of the bark of cherry or birch branches 
two or more years old. Sketch the roundish or oval spongy lenticels 
on the outer surface of the bark. How far in do they extend ? Exam- 
ine (&) the green layer of bark as shown in twigs or branches of 
Forsythia, cherry, alder, box-elder, wahoo, or willow. Examine (c) 
the white, fibrous inner layer, known as hard hast, of the bark of 
elm, leatherwood, pawpaw, or basswood. 

101. Minute Structure of the Dicotyledonous Stem. — Study, first 
with a low and then with a medium power of the compound micro- 
scope, thin cross-sections of clematis-stem cut just before the end of 



STRUCTURE OF THE STEM 



87 



the first season's growth.^ Sketch the whole section without much 
detail, and then make a detailed drawing of a sector running from 
center to circumference and just wide enough to include one of the 
large bundles. Label these drawings in general like Figs. 55, 56. 




■/'^ 



Fig. 55. 



Diagrammatic Cross-Section of an Annual Dicotyledonous Stem. 
(Somewhat magnified.) 



p, pith ; fv, woody or fibro-vascular bundles ; e, epidermis ; b, bundles of hard 
bast fibers of the bark. 




Fig. 56. 



■Diagrammatic Cross-Section of One- Year-Old AristolocMa Stem. 
(Considerably magnified.) 



e, region of epidermis ; b, hard bast ; o, outer or bark part of a bundle (the 
cellular portion under the letter) ; w, inner or woody part of bundle ; c, cam- 
bium layer ; p, region of pith ; to, a medullary ray. 

The space between the hard bast and the bundles is occupied by thin-walled, 
somewhat cubical cells of the bark. 



1 Clematis virginiana is simpler in structure than some of the other woody 
species. AristolocMa sections will do very well. 



88 



FOUNDATIONS OF BOTANY 



Note 



(a) The general outline of the section. 

(&) The number and arrangement of the bundles. (How 
many kinds of bundles are there V) 

(c) The comparative areas occupied by the woody part of the 

bundle and by the part which belongs to the bark. 

(d) The way in which the pith and the outer bark are con- 

nected (and the bundles separated) by the medullary rays. 



d< 




Fig. 57. — One Bundle from the Preceding Figure, (x 100.) 

w, wood-cells ; d, ducts. The other letters are as in Fig. 56. Many sieve-cells 

occur in the region just outside of the cambium of the bundle. 



Examine a longitudinal section of the same kind of stem, to find 
out more accurately of what kinds of cells the pith, the bundles, and 
the outer bark are built. AVhich portion has cells that are nearly 
equal in shape, as seen in both sections ? 



STRUCTURE OF THE STEM 



89 



102. Mechanical Importance of Distribution of Material 
in the Dicotyledonous Stem. — It is easy to see that those 
tissues which are tough, like hard bast, and those which 
are both tough and stiff, like wood fibers, are arranged in 
a tubular fashion in young dicotyledonous stems as they 
are in some monocotyledonous ones (Fig. 53). Sometimes 
the interior of the stem is quite hollow, as, for example, 



B 



mimm^h 











Fig. 58. — stem of Box-Elder One Year Old. (Much magnified.) 
A, lengthwise (radial) section ; B, cross-section ; e, epidermis ; clc, cork ; b, hard 
bast ; s, sieve-cells ; c, cambium ; w, wood-cells ; m, medullary rays ; d, 
ducts ; p, pith. 

in the stems of balsams, melons, cucumbers, and squashes, 
and in the flower-stalks of the dandelion. In older stems, 
such as the trunks of trees, the wood forms a pretty nearly 
solid cylinder. 

Stiffness in dicotyledonous stems is secured mainly in 
two ways : (1) by hard bast fibers, (2) by wood fibers. 
Which of these types does the stem (Fig. 55) represent? 
Which does the flax-stem (Fig. 60) represent? 



90 FOUNDATIONS OF BOTANY 

Notice that in both types bast fibers and wood fibers are 
present, but the proportions in (1) and (2) vary greatly. 

103. Kinds of Cells which compose Stems. — The stu- 
dent has already seen something of cells in the seed, in 
the roots of seedlings and mature plants, and in several 
kinds of stems. But he will need to become acquainted 
with a much larger variety of cells in the stem. The fol- 
lowing materials will serve to* illustrate some of the most 
important forms. ^ 

Examine with a half-inch objective and one-inch eyepiece (or 
higher power) these preparations (1-9 below) : 

Study very carefully each of the sections described, find in it 
the kind of cell referred to in the corresponding number (1-9) of 
the following section (104), and make a good sketch of a group of 
cells of each kind as actually seen under the microscope.^ 

(1) Very thin sections of the epidermis of a potato, some cut parallel 
to the surface (tangential), others cut at right angles to the epidermis. 

(2) Thin sections of the green layer of tlie bark of Forsythia, 
spindle tree (Euonymus), or box-elder {Negundo). 

(3) Thin cross-sections and longitudinal sections of the inner bark 
of linden twigs, or of full-grown stems of flax. 

(4) Longitudinal sections of the stem of squash or cucumber plants. 

(5) Thin cross-sections of young twigs of pine or oak, cut in late 
summer. 

(6) Thin cross-sections and longitudinal sections, cut from pith 
toward bark (radial) of young wood of sycamore, of sassafras, or of 
box -elder. 

(7) Thin longitudinal sections of the stem of castor-oil plant 
(Ricinus) or of the stalk (peduncle) on which the fruit of the 
banana is supported. 

1 These studies may be made from sections cut by the pupil, by the teacher, or 
by a professional hand, as circumstances may dictate. The soft bast (No. 4, see 
p. 91) can best be studied in good prepared sections obtained of the dealers. 

2 Nothing can do so much to make these studies valuable as for the teacher 
to correct in class the errors of most frequent occurrence in the drawings, by 
aid of his own camera lucida drawings of the same objects. 



STRUCTURE OF THE STEM 



91 



(8) Thin longitudinal radial sections of sycamore, of sassafras, 
maple, or box-elder wood. 

(9) Thin sections of elder pith, sunflower-stem pith, or of so-called 
Japanese " rice-paper." 



104. Names of the Cells of Bark, Wood, and Pith. — No 

two varieties of stems will be found to consist of just the 

l\ 



B 



^^ 



/ 
D 

Fig. 59. — ^, B, C, 
D, Isolated Wood- 
Cells and Bast- 
Cells of Linden. 

^,^, wood fibers ; C, 
piece of a vessel; 
D, bast fiber ; E, a 
partitioned, woody 
fiber from Euro- 
pean ivy. (Mucb 
magnified.) 

(4) Soft bast 
greatly 




Fig. 60. — Part of Cross-Section of Stem of Flax. 
(Much magnified.) 

e, epidermis ; b, hard bast ; s, sieve-cells ; iv, wood. 

same kinds of cells, present in the same 
proportions, but it is easy to refer to illus- 
trations which will serve to identify the 
kinds of cells found in the studies of the 
preceding section. They are : 

(1) Cork-cells of the epidermis ' (e.g., flax. 
Fig. 60, e). 

(2) Cells of the green bark (e.g., flax, Fig. 60), 
between b and e. 

(3) Hard bast (Fig. 60). 
(e.g., flax, Fig. 60, s, for the cross-section and (very 
magnified) Figs. 63, 64, for the lengthwise section).^ 



1 The sieve-tubes shown in these figures are only one of several kinds of 
cell found in soft bast, but they are the most peculiar and characteristic ones. 
(See Strasburger, Noll, Schenk, and Schimper's Text-Book, pp. 102-104.) 



92 



FOUNDATIONS OF BOTANY 



(5) Cambium (e.g., Fig. 57, c). 

(6) Wood-cells {e.g., Figs. 58, 72-73). 

(7) Vessels or ducts (e.g., Figs. 58 and 62). 

(8) Wood parenchyma {e.g., Figs. 58 and 72 in the medullary 

rays). 

(9) Pith {e.g.y Figs. 55, 57). 

105. Structure of Coniferous Wood In the wood of 

the cone-bearing trees of the pine family regular ducts or 





Fig. 61. Fig. 62. 

Fig. 61. — A Group of Hard Bast Fibers, (Greatly magnified.) 
a, cut-off ends ; 6, lengthwise section of fibers. 

Fig, 62. — A Lengthwise Section (greatly magnified) of a Group of Spiral Vessels 
from the Stem of Sunfiower, At the top of the figure some of the spiral 
threads which line the vessels are seen partly uncoiled. 

vessels are lacking. The main bulk of the wood is com- 
posed of long cells (often called tracheids), marked with 



STRUCTUEE OF THE STEM 



93 



peculiar pits. These pits, when young, are shaped much 
like two perforated watch-glasses, placed against a piece 
of cardboard, with their concave sides toward each other 




Fig. 63. Fig. 64. 

Fig. 63. — Part of a Sieve-Tube from Linden. 
s, sieve-plates on the cell-wall, (x about 900.) 

Fig. 64. — Parts of Sieve-Tubes as found in Plants of the Gourd Family, 
(Greatly magnified.) 

s, s, a sieve-plate seen edgewise ; above it a similar one, surface view. 

Fig. 65. —Cross-Section of Fir Wood, 
s, a resin passage ; m, medullary rays. (Much magnified.) 



94 



FOUNDATIONS OF BOTANY 



(see Fig. 66, t''). The cardboard represents a part of the 
cell-wall common to two adjacent cells, and the watch- 
glasses are like the convex border bulging into each cell. 

When the cells grow old the 
partition jn each pit very com- 
monly breaks away and leaves 
a hole in the cell-wall. 

106. Tissues. — A mass of 
similar cooperating cells is called 
a tissue.'^ Two of the principal 
classes which occur in the stem 
are parenchymatous tissue and 
proseneJiymatous tissue. Paren- 
chyma is well illustrated by the 
green layer of the bark, by wood 
parenchyma, and by pith. Its 
cells are usually somewhat 
roundish or cubical, at any rate 
not many times longer than wide, 
and at first pretty full of proto- 
plasm. Their walls are not 
generally very thick.^ Prosen- 
chyma^ illustrated by hard bast 
and masses of wood-cells, con- 
sists of thick-walled cells many 
times longer than wide, containing little protoplasm and 
often having little or no cell-cavity. 

As a rule the stems of the most highly developed plants 
owe their toughness and their stiffness mainly to prosen- 




FlG. 66. — Longitudinal Radial Sec- 
tion through a Eapidly Growing 
Young Branch of Pine. 

t, f, t", bordered pits on wood-cells ; 
st, large pits where medullary 
rays lie against wood-cells. 
(Much magnified.) 



1 See Vines' Students' Text-Book of Botany, London, 1894, pp. 131-144. 

2 Excepting when they are dead and emptied, like those of old pith. 



STRUCTURE OF THE STEM 



95 




Fia. 67o — Collenchymatous 
and Other Tissue from Stem 
of Balsam {Impatiens). 

e, epidermis ; c, collenchyma; 
i, intercellular spaces be- 
tween large parenchyma- 
cells. 



chymatous tissue. In some (particu- 
larly in fleshy) stems the stiffness is, 
however, largely due to collenchyma^ a 
kind of parenchyma in which the cells 
are thickened or reinforced at their 
angles, as shown in Fig. 6T. 

107. Early History of Stem-Struc- 
ture. — In the very young parts of 
stems, such, 



lor instance, 
as the grow- 
ing point 
between the 
two rudi- 
mentary leaves of a bean-plumule, 
the cells are all of thin-walled 
formative tissue and look a good 
deal alike. This condition of 
things is quickly succeeded by 
one in which there is a cylinder 
(appearing in cross-sections of the 
stem as a ring) of actively growing 
tissue X (Fig. 68, J.), lying between 
the cortex r and the pith m. Soon 
the cylinder x develops into a 
series of separate fibro-vascular 
bundles arranged as shown in 
Fig. 68, B^ and these again in a 
short time unite, as shown at C. 
A comparison of this last portion 
of the figure with that of the 




Fig. 68. — Transverse Section 
through the Hypocotyl of the 
Castor-Oil Plant at Various 
Stages. 

A, after the root has just ap- 
peared outside the testa of the 
seed; B, after the hypocotyl is 
nearly an inch long; C, at the 
end of germination ; r, cortex 
(undeveloped bark) ; m, pith ; 
st, medullary rays ; fv, fibro- 
vascular bundles ; ch, layer of 
tissue which is to develop into 
cambium. (Considerably mag- 
nified.) 



96 FOUNDATIONS OF BOTANY 

one-year-old Aristolochia-stem (Fig. bQ) shows a decided 
similarity between tlie two. In both cases we have the 
central pith, the regularly grouped bundles, and cambium 
(or in Fig. 68, C, a tissue which will grow into cambium), 
— part of it in the bundles and part of it between them. 

In the young monocotyledonous stem the grouping of 
the bundles is less regular than that just explained. This 
is shown by Fig. 52. A much more important difference 
consists in the fact that the monocotyledonous stem has 
usually no permanent living cambium ring. Annual dicoty- 
ledons, however, are also destitute of permanent cambium. 

108. Secondary Growth. — From the inside of the cam- 
bium layer the wood-cells and du3ts of the mature stem 
are produced, while from its outer circumference proceed 
the new layers of the inner bark, composed largely of sieve- 
cells and hard bast. From this mode of increase the stems 
of dicotyledonous plants are called exogenous, that is, out- 
side-growing. The presence of the cambium layer on the 
outside of the wood in early spring is a fact well known 
to the schoolboy, who pounds the cylinder cut from an 
elder, willow, or hickory branch until the bark will slip 
off and so enable him to make a whistle. The sweet taste 
of this pulpy layer, as found in the white pine, the slippery 
elm, and the basswood, is a familiar evidence of the 
nourishment which the cambium layer contains. 

With the increase of the fibro-vascular bundles of the 
wood the space between them, which appears relatively 
large in Fig. 68, becomes less and less, and the pith, which 
at first extended freely out toward the circumference of 
the stem, is at length only represented by thin plates, the 
medullary rays. 



STEUCTURE OF THE STEM 



97 



These are of use in storing the food which the plant 
in cold and temperate climates lays up in the summer and 
fall for use in the following spring, and in the very young 
stem they serve as an important channel for the transfer- 
ence of fluids across the stem from bark to pith, or in the 




Fig. 



Diagram to illustrate Secondary Growth in a Dicotyledonous Stem. 



R, the first-formed bark ; p, mass of sieve-cells ; ifp, mass of sieve-cells between 
the original wedges of wood ; fc, cambium of wedges of wood ; ic, cambium 
between wedges ; b, groups of bast-cells ; fh, Avood of the original wedges ; 
ifh, wood formed between wedges ; x, earliest wood formed ; M, pith. 

reverse direction. On account, perhaps, of their impor- 
tance to the plants, the cells of the medullary rays are 
among the longest lived of all plant-cells, retaining 
their vitality in the beech tree sometimes, it is said, for 
more than a hundred years. 

After the interspaces between the first fibro-vascular 
bundles have become filled up with wood, the subsequent 



98 FOUNDATIOI^S OF BOTANY 

growth must take place in the manner shown in Fig. 69. 
All the cambium, both that of the original wedges of wood, 
/(?, and that, ic, formed later between these wedges, con- 
tinues to grow from its inner and from its outer face, and 
thus causes a permanent increase in the diameter of the stem 
and a thickening of the bark, which, however, usually at 
an early period begins to peel off from the outside and 
thus soon attains a pretty constant thickness.^ It will be 
noticed, in the study of dicotyledonous stems more than a 
year old, that there are no longer any separate fibro-vascular 
bundles. The process just described has covered the origi- 
nal ring of bundles with layer after layer of later formed 
wood-cells, and the wood at length is arranged in a hollow 
cylinder. 

It is the lack of any such ring of cambium as is found 
in dicotyledonous plants, or even of permanent cambium 
in the separate bundles, that makes it impossible for the 
trunks of most palm trees (Fig. 54) to grow indefinitely 
in thickness, like that of an oak or an elm.^ 

109. Grafting. — When the cambium layer of any vigor- 
ously growing stem is brought in contact with this layer 
in another stem of the same kind or a closely similar kind 
of plant, the two may grow together to form a single stem 
or branch. This process is called grafting, and is much 
resorted to in order to secure apples, pears, etc., of any 
desired kind. A twig from a tree of the chosen variety is 
grafted on to any kind of tree of the same species (or some- 
times a related species), and the resulting stems will bear 
the wished-for kind of fruit. Sometimes grafting comes 

1 See Vines' Students' Text-Book of Botany, London, 1894, pp. 211, 212. 

2 See, however, Stra.sburger, Noll, Schenk and Schimper's Text-Book, 
pp. 138, 139. 



STRUCTURE OF THE STEM 



99 



about naturally by the branches of a tree chafing against one 
another until the bark is worn away and the cambium layer 
of each is in contact with that of the other, or two separate 
trees may be joined by 
natural grafting, as is 
shown in Fig. 70. 

110. Stem-Structure 
of Climbing Shrubs. — 
Some of the most remark- 
able kinds of dicotyle- 
donous stems are found 
in climbing shrubs. The 
structure of many of 
these is too complicated 
to be discussed in a 
botany for beginners, but 
one point in regard to 
them is of much inter- 
est. The bundles (as 
seen in the clematis and 
shown in Fig. 56) are 
much more distinct than 
in most other woody 
stems. Even after sev- 
eral years of growth the 
wood is often found to be 
arranged in a number of 
flattish twisted strands. 
It is evident that this is for the sake of leaving the 
stem flexible for twining purposes, just as a wire cable is 
adapted to be wound about posts or other supports, while 




Fig. 70. — Two Ash Trees naturally 
grafted together. 



L.oFC. 



100 



FOUNDATIONS OF BOTANY 



Phi 



a solid steel or iron rod of the same size would be too 
stiff for this use. 

111. The Dicotyledonous Stem, thickened by Secondary Growth. — 

Cut off, as smoothly as possible, a small branch of hickory and one of 
white oak above and below each of the rings of scars already mentioned 

(Sect. 77), and count the 
rings of wood above and 
below each ring of scars. 

How do the numbers 
correspond? What does 
this indicate ? 

Count the rings of 
wood on the cut-off ends 
of large billets of some 
of the following woods : 
locust, chestnut, syca- 
more, oak, hickory. 

Do the successive rings 
of the same tree agree in 
thickness ? 

Why ? or why not ? 

Does the thickness of 
the rings appear uniform 
all the way round the stick 
of wood? If not, the rea- 
son in the case of an up- 
right stem (trunk) is per- 




JR 



IR 



Fig. 71. — Cross-Section of a Tliree-Year-Old 
Linden Twig. (Much magnified.) 
P, epidermis and corky layer of thetark ; Phi, bast ; 
C, cambium layer ; JR, annual rings of wood. 



haps that there was a greater spread of leaves on the side where the 
rings are thickest ^ or because there was unequal pressure, caused by 
bending before the wind. 

Do the rings of any one kind of tree agree in thickness with 
those of all the other kinds ? What does this show ? 

In all the woods examined look for : 

(a) Contrasts in color between the hea.rtwood and the sapwood.^ 

1 See Sect. 118. 

2 This is admirably shown in red cedar, black walnut, barberry, black 
locust and osage orange. 



STRUCTURE OF THE STEM 



101 



(b) The narrow lines running in very young stems pretty straight 
from pith to bark, in older wood extending only a little of the way 
from center to bark, the medullary rays, shown in Fig. 72.i 

(c) The wedge-shaped masses of wood between these. 

(c/) The pores which are so grouped as to mark the divisions 
between successive rings. These pores indicate the cross-sections of 

vessels or ducts. Note the dis- 
tribution of the vessels in the 
rings to which they belong, com- 





FiG. 72. — Cross-Section of Beech-Wood. 
b, bark ; a, flattened cells formed near 
end of each year's growth ; w, regu- 
lar wood-cells ; m, medullary ray. 



Fig. 73. —Longitudinal Section of 
Mahogany at Right Angles to 
Medullary Rays, showing Cut- 
off Ends. (Much magnified.) 



pare this with Figs. 58, 72, and decide at what season of the year 
the largest ducts are mainly produced. Make a careful drawing 
of the end-section of one billet of wood, natural size. 

Cut off a grapevine several years old and notice the great size of 



1 These and many other important things are admirably shown in the thin 
wood-sections furnished for $4 per set of 24 by R. B. Hough, Lowville, N. Y. 



102 



FOUNDATIONS OE BOTANY 



the vessels. Examine the smoothly planed surface of a billet of red 
oak that has been split through the middle of the tree (quartered 
oak), and note the large shining plates formed 
by the medullary rays. 

Look at another stick that has been planed 
away from the outside until a good-sized flat 
surface is shown, and see how the medullary 
rays are here represented only by their 
edges. 

112. Interruption of Annual Rings by 
branches ; Knots. — When a leaf -bud is 
formed on the trunk- or branch of a 
dicotyledonous tree, it is connected with 
the wood by fibro-vascular bundles. As 
the bud develops into a branch, the few 
bundles which it originally possessed 
increase greatly in number, and at 
length, as the branch grows, form a 
cylinder of wood which cuts across the 
annual rings, as shown in Fig. 74. 
This interruption to the rings is a knot, 
such as one often sees in boards and 
planks. If the branch dies long before 
the tree does, the knot may be buried under many rings 
of wood. What is known as clear lumber is obtained 
from trees that have grown in a dense forest, so that the 
lower branches of the larger trees were killed by the shade 
many years before the tree was felled. 

In pruning fruit trees or shade trees the branches 
which are removed should be cut close to the trunk. If 
this is done, the growth of the trunk will bury the scar 
before decay sets in. 




Fig. 74. — Formation of 
a Knot in a Tree- 
Trunk. 

R, cut-off end of stick, 
showing annual rings ; 
K, knot, formed by 
growth of a branch. 



STRUCTURE OF THE STEM 



103 



113. Comparison of the Monocotyledonous and the Dicotyledonous 
Stem.i 

Monocotyledonous Dicotyledonous 

Stem Stem 



General Structure. 



Structure of 
Bundles. 

Growth in Thick- 
ness. 



A hard rind of 
rather uniform struc- 
ture. Bundles inter- 
mixed with the pith. 



Bundles closed, 
that is, without per- 
manent cambium. 

Cells of mature 
parts of stem expand 
somewhat, but (in 
most palms) new ones 
are not found. 



A complex bark, 
usually on young- 
shoots consisting of 
a corky layer, a green 
layer, and a layer of 
bast. Wood in an- 
nual rings. Pith in 
a cylinder at the cen- 
ter. 

Bundles open, with 
permanent cambium. 

New wood-cells 
formed throughout 
growing season from 
cambium ring. 



114'. Review Sketches and Diagrams. 

(1) Monocotyledonous stem (lengthwise section). 

(2) Dicotyledonous stem (lengthwise section). 

(3) First appearance of bundles in dicotyledonous stem. 

(4) Dicotyledonous stem five years or more old (cross-section). 

(5) Various bark-cells. 

(6) Various cells from wood. 

(7) Pith-cells. 

(8) Collenchyma-cells. 



1 This comparison applies only to most of the woody or tree-like stems. 



CHAPTER VTI 
LIVING PARTS OF THE STEM; WORK OF THE STEM 

115. Active Portions of the Stems of Trees and Shrubs. 

— In annual plants generally and in the very young 
shoots of shrubs and trees there are stomata or breathing 
pores which occur abundantly in the epidermis, serving 
for the admission of air and the escape of moisture, while 
the green layer of the bark answers the same purpose that 
is served by the green pulp of the leaf (Chapter XI). 
For years, too, the spongy lenticels, which succeed the 
stomata and occur scattered over the external surface of 
the bark of trees and shrubs, serve to admit air to the 
interior of the stem. The lenticels at first appear as 
roundish spots, of very small size, but as the twig or shoot 
on which they occur increases in diameter the lenticel 
becomes spread out at light angles to the length of the 
stem, so that it sometimes becomes a longer transverse slit 
or scar on the bark, as in the cherry and the birch. But 
in the trunk of a large tree no part of the bark except the 
inner layer is alive. The older portions of the bark, such 
as the highly developed cork of the cork-oak, from which 
the ordinary stoppers for bottles are made, sometimes 
cling for years after they are dead and useless except as a 
protection for the parts beneath against mechanical injuries 
or against cold. But in many cases, as in the shell-bark hick- 
ory and the grapevine, the old bark soon falls off in strips ; 
ill birches it finally peels off in bands around the stem. 

104 



LIVING PARTS OF THE STEM 105 

The cambium layer is very much alive, and so is the 
young outer portion of the wood. Testing this "sap- 
wood," particularly in winter, shows that it is rich in 
starch and proteids. 

The heartwood of a full-grown tree is hardly living, 
unless the cells of the medullary rays retain their vitality, 
and so it may be that wood of this kind is useful to the 
tree mainly by giving stiffness to the trunk and larger 
branches, thus preventing them from being easily broken 
by storms. 

It is, therefore, possible for a tree to flourish, sometimes 
for centuries, after the heartwood has much of it rotted 
away and left the interior of the trunk hollow, as shown 
in Fig. 75. 

116. Uses of the Components of the Stem. — There is a 
marked division of labor among the various groups of cells 
that make up the stem of ordinary dicotyledons, particu- 
larly in the stems of trees, and it will be best to explain 
the uses of the kinds of cells as found in trees, rather than 
in herbaceous plants. A few of the ascertained uses of 
the various tissues are these: 

The pith forms a large part of the bulk of very young 
shoots, since it is a part of the tissue of comparatively 
simple structure amid which the fibro-vascular bundles 
arise. In mature stems it becomes rather unimportant, 
though it often continues for a long time to act as a store- 
house of food. 

The medullary rays in the young shoot serve as a chan- 
nel for the transference of water and plant-food in a liquid 
form across the stem, and they often contain much stored 
food. 



106 



FOUNDATIONS OF BOTANY 




Fig. 75. — Pioneer's Cabin, a Very Large Hollow Sequoia. 

The vessels carry water upward and (sometimes) air 
downward through the stem. 

The wood-cells of the heartwood are useful only to give 



LIVING PARTS OF THE STEM 107 

stiffness to the stem. Those of the sapwood, in addition 
to this work, have to carry most of the water from the 
roots to the leaves and other distant portions of tlie plant. 

The cambium layer is the region in which the annual 
growth of the tree takes place (Figs. 69, 71). 

The most important portion of the inner bark is that 
which consists of sieve-tubes, for in these digested and 
elaborated plant-food is carried from the leaves toward the 
roots. 

The green layer of the bark in young shoots does much 
toward collecting nutrient substances, or raw materials, 
and preparing the food of the plant from air and water, 
but this work may be best explained in connection with 
the study of the leaf (Chapter XI). 

117. Movement of Water in the Stem. — The student 
has already learned that large quantities of water are taken 
up by the roots of plants. 

Having become somewhat acquainted with the structure 
of the stem, he is now in a position to investigate the 
question how the various fluids, commonly known as sap, 
travel about in it.^ It is important to notice that sap is 
by no means the same substance everywhere and at all 
times. As it first makes its way by osmotic action inward 
through the root-hairs of the growing plant it differs but 
little from ordinary spring water or well water. The 
liquid which flows from the cut stem of a " bleeding " 
grapevine which has been pruned just before the buds 
have begun to burst in the spring, is mainly water with a 
little dissolved mucilaginous material. The sap which is 

1 See the paper on " The So-called Sap of Trees and its Movements," by 
Professor Charles R. Barnes, Science, Vol. XXI, p. 535. 



108 



FOUNDATIONS OF BOTANY 



obtained from maple trees in late winter or early spring, 
and is boiled down for syrup or sugar, is still richer in 
nutritious material than the water of the grapevine, while 
the elaborated sap which is sent so abundantly into the ear 
of corn, at its period of filling out, or into the growing 
pods of beans and peas, or into the rapidly forming acorn 
or the chestnut, contains great stores of food, suited to sus- 
tain plant or animal life. 



EXPERIMENT XXI 

Rise of Water in Stems. — Cut some short branches from an 
apple tree or a cherry tree and stand the lower end of each 
in red ink; try the same experiment with twigs of oak, 
or 



other porous wood, 




Fig. 76. — a Cutting girdled and 
sending down Roots from tlie 
Upper Edge of the Girdled Ring. 



ash, 
and after some hours ^ examine with 
the magnifying glass and with the 
microscope, using the 2-inch objective, 
successive cross-sections of one or more 
twigs of each kind. Note exactly the 
portions through which the ink has 
traveled. Pull off the leaves from one 
of the stems after standing in the eosin 
solution, and notice the spots on the 
leaf -scar through which the eosin has 
traveled. These spots show the posi- 
tions of the leaf-traces, or fibro-vascular 
bundles, connecting the stem and the 
leaf. Repeat with several potatoes, cut 
crosswise through the middle. Try 
also some monocotyledonous stems, 
such as those of the lily or asparagus. 
For the sake of comparison between 
roots and stems, treat any convenient 
root, such as a parsnip, in the same way. 



i If the twigs are leafy and the room is warm, only from 5 to 30 minutes 
may be necessary. 



LIVING PARTS OF THE STEM 



109 



Examine longitudinal sections of some of the twigs, the potatoes, 
and the roots. In drawing conclusions about the channels through 
which the ink has risen (those through which the newly absorbed 
soil-water most readily trav- 
els), bear in mind the fact 
that a slow soakage of the 
red ink will take place in 
all directions, and therefore 
pay attention only to the 
strongly colored spots or 
lines. 

What conclusions can be 
drawn from this experiment 
as to the course followed by 
the sap? 

From the familiar 
facts that ordinary for- 
est trees apparently 
flourish as well after the 
almost complete decay 
and removal of their 
heartwood, and that 
many kinds will live 
and grow for a consider- 

, , . p . n. Fig. 77. — Channels for the Movement of 

able time alter a rmg OI water, upward and downward. 

bark extending all round The heavy black Imes in roots, stems, and 
, 1 u "U leaves show the course of the fibro-vascular 

trie truuE: nas been re- bundles through which the principal move- 
moved, it may readily be ™®"*^ «^ '^^**'^' *^^® p^^«^- 
inferred that the crude sap in trees must rise through some 
portion of the newer layers of the wood. A tree girdled 
by the removal of a ring of sapwood promptly dies. 

118. Downward Movement of Liquids. — Most dicoty- 
jledonous stems, when stripped of a ring of bark and then 




110 



FOUNDATIONS OF BOTANY 



stood in water, as shown in Fig. 
bell-jar, develop roots only at or 




Fig. 78. — Diagrammatic Cross-Section of a 
Bundle from Sugar-Cane, showing Channels 
for Air and Water. (Magnified.) 

Air travels downward through the two large 
ducts d (and the two smaller ones between 
them). Water travels iipward through the 
ducts and through the wood-cells in the 
region marked w. Water with dissolved 
plant-food travels downward through the 
sieve-cells in the region marked s. 



76, and covered with a 
near the upper edge of 
the stripped portion,^ 
and this would seem to 
prove that such stems 
send their building ma- 
terial — the elaborated 
sap — largely at any rate 
down through the bark. 
Its course is undoubt- 
edly for the most part 
through the sieve-cells 
(Figs. 63, 64), which are 
admirably adapted to 
convey liquids. In ad- 
dition to these general 
upward and downward 
movements of sap, there 
must be local transfers 



laterally through the stem, and 
these are at times of much im- 
portance to the plant. 

Since the liquid building mate- 
rial travels straight down the 
stem, that side of the stem on 
which the manufacture of such 
material is going on most rapidly should grow fastest 




Fig. 79. —Unequal Growth of Rings 
of Wood in nearly Horizontal 
Stem of a Juniper. (Natural size.) 



1 This may be made the subject of a protracted class-room experiment. 
Strong shoots of willow should be used for the purpose. 



LIVING PARTS OF THE STEM 111 

Plant-food is made out of the raw materials by the leaves, 
and so the more leafy side of a tree forms thicker rings 
than the less leafy side, as shown in Fig. 79. 

119. Rate of Movement of Water in the Stem. — There 
are many practical difficulties in the way of ascertaining 
exactly how fast the watery sap travels from the root to 
the leaves. It is, however, easy to illustrate experimen- 
tally the fact that it does rise, and to give an approximate 
idea of the time required for its ascent. The best experi- 
ment for beginners is one which deals with an entire 
plant under natural conditions. 

EXPERIMENT XXII 

Wilting and Recovery, — Allow a fuchsia or a hydrangea ^ which 
is growing in a flower-pot to wilt considerably for lack of watering. 
Then water it freely and record the time required for the leaves to 
begin to recover their natural appearance and position, and the 
time fully to recover. 

The former interval of time will give a very rough idea 
of the time of transfer of water through the roots and the 
stem of the plant. From this, by measuring the approxi- 
mate distance traveled, a calculation could be made of the 
number of inches per minute that water travels in this 
particular kind of plant, through a route which is partly 
roots, partly stem, and partly petiole. Still another 
method is to treat leafy stems as the student in Exp. XXI 
treated the twigs which he was examining, and note care- 
fully the rate of ascent of the coloring liquid. This plan 
is likely to give results that are too low, still it is of some 
use. It has given results varying from 34 inches per 

1 Hydrangea Hortensia. 



112 FOUNDATIONS OF BOTANY 

hour for the willow to 880 inches per hour for the sun- 
flower. A better method is to introduce the roots of the 
plant which is being experimented upon into a weak 
solution of some chemical substance which is harmless to 
the plant and which can readily be detected anywhere in 
the tissues of the plant by chemical tests. Proper tests 
are then applied to portions of the stem which are cut 
from the plant at short intervals of time. 

Compounds of the metal lithium are well adapted for 
use in this mode of experimentation. 

120. Causes of Movements of Water in the Stem. — Some 
of the phenomena of osm^osis were explained in Sect. 62, 
and the work of the root-hairs was described as due to 
osmotic action. 

Koot-pressure (Sect. 6Q), being apparently able to sus 
tain a column of water only 80 or 90 feet high at the 
most, and usually less than half this amount, would be 
quite insufficient to raise the sap to the tops of the tallest 
trees, since many kinds grow to a height of more than 100 
feet. Our Californian "big trees," or Sequoias, reach 
the height of over 300 feet, and an Australian species of 
Eucalyptus, it is said, sometimes towers up to 470 feet. 
Root-pressure, then, may serve to start the soil-water on 
its upward journey, but some other force or forces must 
step in to carry it the rest of the way. What these other 
forces are is still a matter of discussion among botanists. 

The slower inward and downward movement of the sap 
may be explained as due to osmosis. For instance, in the 
case of growing wood-cells, sugary sap descending from the 
leaves into the stem gives up part of its sugar to form 
the cellulose of which the wood-cells are being uade. 



LIVING PARTS OF THE STEM 113 

This loss of sugar would leave the sap rather more 
watery than usual, and osmosis would carry it from the 
growing wood to the leaves, while at the same time a slow 
transfer of the dissolved sugar will be set up from leaves 
to wood. The water, as fast as it reaches the leaves, will 
be thrown off in the form of vapor, so that they will 
not become distended with water, while the sugar will be 
changed into cellulose and built into new wood-cells as fast 
as it reaches the region where such cells are being formed. 

Plants in general ^ readily change starch to sugar, and 
sugar to starch. When they are depositing starch in any 
part of the root or stem for future use, the withdrawal of 
sugar from those portions of the sap which contain it 
most abundantly gives rise to a slow movement of dis- 
solved particles of sugar in the direction of the region 
where starch is being laid up. 

121. Storage of Food in the Stem. — The reason why the 
plant may profit by laying up a food supply somewhere 
inside its tissues has already been suggested (Sect. 91). 

The most remarkable instance of storage of food in the 
stem is probably that of sago-palms, which contain an 
enormous amount, sometimes as much as 800 pounds, of 
starchy material in a single trunk. But the commoner 
plants of temperate regions furnish plenty of examples of 
deposits of food in the stem. As in the case of seeds and 
roots, starch constitutes one of the most important kinds 
of this reserve material of the stem, and since it is easier 
to detect than any other food material which the plant 
stores, the student will do well to spend time in looking 
for starch only. 

1 Not including most of the flowerless and very low and simple kinds. 



114 FOUNDATIONS OF BOTANY 

Cut thin cross-sections of twigs of some common deciduous tree 
or shrub, in its early winter condition, moisten with iodine solution, 
and examine for starch with a moderately high power of the micro- 
scope. Sketch the section with a pencil, coloring the starchy por- 
tions with blue ink, used with a mapping pen, and describe exactly 
in what portions the starch is deposited. 

122. Storage in Underground Stems. — The branches 
and trunk of a tree furnish the most convenient place 
in which to deposit food during winter to begin the 
growth of the following spring. But in those plants 
which die down to the ground at the beginning of winter 
the storage must be either in the roots, as has been 
described in Sect. 58, or in underground portions of 
the stem. 

Rootstocks, tubers, and bulbs seem to have been de- 
veloped by plants to answer as storehouses through the 
winter (or in some countries through the dry season) for 
the reserve materials which the plant has accumulated 
during the growing season. The commonest tuber is the 
potato, and this fact and the points of interest which it 
represents make it especially desirable to use for a study 
of the underground stem in a form most highly specialized 
for the storage of starch and other valuable products. 

123. A Typical Tuber : the Potato. — Sketch the general outline 
of a potato, showing the attachment to the stem from which it grew.^ 

Note the distribution of the "eyes," — are they opposite or alter- 
nate ? Examine them closely with the magnifying glass and then with 
the lowest power of the microscope. What do they appear to be ? 

If the potato is a stem, it may branch, — look over a lot of pota- 
toes to try to find a branching specimen. If such a one is secured, 
sketch it. 

1 Examination of a lot of potatoes will usually discover specimens with an 
inch or more of attached stem. 



LIVING PARTS OF THE STEM 115 

Note the little scale overhanging the edge of the eye, and see if 
you can ascertain what this scale represents. 

Cut the potato across, and notice the faint broken line which 
forms a sort of oval figure some distance inside the skin. 

Place the cut surface in eosin solution, allow the potato to stand 
so for many hours, and then examine, by slicing off pieces parallel 
to the cut surface, to see how far and into what portions the solution 
has penetrated. Refer to the notes on the study of the parsnip 
(Sect. 56), and see how far the behavior of the potato treated with 
eosin solution agrees with that of the parsnip so treated. 

Cut a thin section at right angles to the skin, and examine with a 
high power. Moisten the section with iodine solution and examine 
again. 

If possible, secure a potato which has been sprouting in a warm 
place for a month or more (the longer the better), and look near 
the origins of the sprouts for evidences of the loss of material from 
the tuber. 

EXPERIMENT XXIII 

Use of the Corky Layer. — Carefully weigh a potato, then pare 
another larger one, and cut portions from it until its weight is made 
approximately equal to that of the first one. Expose both freely to 
the air for some days and rew.eigh. What does the result show in 
regard to the use of the corky layer of the skin? 

124. Morphology of the Potato. — It is evident that in 
the potato we have to do with a very greatly modified 
form of stem. The corky layer of the bark is well repre- 
sented, and the loose cellular layer beneath is very greatly 
developed ; wood is almost lacking, being present only in 
the very narrow ring which was stained by the red ink, 
but the pith is greatly developed and constitutes the prin- 
cipal bulk of the tuber. All this is readily understood if 
we consider that the tuber, buried in and supported by 
the earth, does not need the kinds of tissue which give 



116 FOUNDATIONS OF BOTANY 

strength, but only those which are well adapted to store 
the requisite amount of food. 

125. Structure of a Bulb ; the Onion. — Examine the external 

appearance of the onion and observe the thin membranaceous skin 
which covers it. This skin consists of the broad sheathing bases of 
the outer leaves which grew on the onipn plant dm-ing the summer. 
Remove these and notice the thick scales (also formed from bases 
of leaves as shown in Fig. 48) which make up the substance of the 
bulb. 

Make a transverse section of the onion at about the middle and 
sketch the rings of which it is composed. Cut a thin section from 
the interior of the bulb, examine with a moderate power of the 
microscope, and note the thin-walled cells, of which it is composed. 

Split another onion from top to bottom and try to find : 

(a) The plate or broad flattened stem inside at the base (Fig. 47). 

(5) The central bud. 

(c) The bulb-scales. 

(d) In some onions (particularly large, irregular ones) the bulblets 
or side buds arising in the axes of the scales near the base. 

Test the cut surface for starch. 

126. Sugar in the Onion Grape sugar is an important 

substance among those stored for food by the plant. It 
received its name from the fact that it was formerly 
obtained for chemical examination from grapes. Old 
dry raisins usually show little masses of whitish material 
scattered over the skin which are nearly pure grape sugar. 
Commercially it is now manufactured on an enormous 
scale from starch by boiling with diluted sulphuric acid. 
In the plant it is made from starch by processes as yet 
imperfectly understood, and another sugar, called maltose^ 
is made from starch in the seed during germination. 

Both grape sugar and maltose (and hardly any other 
substances) have the power of producing a yellow or 



LIVING PARTS OF THE STEM 117 

orange color and throwing down an orange or reddish 
deposit, when they are added to a brilliant blue alkaline 
solution of copper, known as Fehling^s solution} The 
color or deposit will not appear until the solution has 
been heated to boiling. 

EXPERIMENT XXIV 

Testing for Grape Sugar. — Heat to boihng in a test-tube or a 
small beaker some weak syrup of grape sugar or some honey, much 
diluted with water. Add Fehling's solution, a few drops at a time, 
until a decided orange color appears. Repeat the test with the 
water in which some slices of onion have been boiled, filtering the 
water through a paper filter and heating again to boiling before 
adding the test solution.^ 

127. Proteids in the Onion. — Since the onion grows 
so rapidly on being planted in the spring, there must be 
a large supply of food in the bulb ; there may be other 
substances present besides sugar. 

EXPERIMENT XXV 

Testing an Onion for Other Stored Food. — Test a rather thick 
slice of onion by heating it in a porcelain evaporating dish with a 
little strong nitric acid until the latter begins to boil and the onion 
becomes somewhat softened.^ Rinse off the slice of onion in a stream 
of water, then pour on it a few drops of ammonium hydrate and 
observe any change of color. What is proved ? See Sect. 29. 

128. Tabular Review of Experiments. 

[Continue the table from Sect. 74.] 

1 For the preparation of the solution see Handbook. 

2 The deposit will in this case, even if orange at first, finally become black, 
probably owing to the presence of sulphur in the onion. 

8 Do not allow the acid to touch the clothing, the hands, or any metallic 
object. 



118 FOUNDATIONS OF BOTANY 

129. Review Summary of Work of Stem. 

C in young dicotyledonous stems 
Channels for upward movement J in dicotyledonous stems several 

of water j years old 

i in monocotyledonous stems . . 

Channels for downward move- f in dicotyledonous stems 

ment of water 1^ in monocotyledonous stems . . 

Channels for transverse movements . 

Rate of upward movement 

{where stored 
kinds stored 
uses 



CHAPTER VIII 
BUDS 

130. Structure of Buds. — While studying twigs in their 
winter condition, as directed in Sects. 77, 78, the student 
had occasion to notice the presence, position, and arrange- 
ment of buds on the branch, but he was not called upon 
to look into the details of their structure. The most natu- 
ral time to do this is just before the study of the leaf is 
begun, since leafy stems spring from buds, and the rudi- 
ments of leaves in some form must be found in buds. 

131. The Horse-Chestnut Bud. — Examine one of the lateral buds 
on a twig in its winter or early spring condition.^ 

Make a sketch of the external appearance of the buds as seen with 

a magnifying glass. i 

How do the scales with which it is | 

covered lie with reference to those | 

beneath them ? I 

N'otice the sticky coating on the scales. 

Are the scales opposite or alternate ? j 

Remove the scales in pairs, placing 5 

them in order on a sheet of paper, thus : | 

Make the distance from 1 to 1 as much i 

as 6 or 8 inches. { 

How many pairs are found? 

Observe as the scales are removed whether the sticky coating is 

1 The best possible time for this examination is just as the buds are begin- 
ning to swell slightly in the spring. The bud. of buckeye or of cottonwood 
will do for this examination, though each is on a good deal smaller scale than 
the horse-chestnut bud. Buds may be forced to open early by placing twigs 
in water in a very warm, light place for many weeks. 

119 



120 



FOUNDATIONS OF BOTANY 



thicker on the outside or the inside of each scale, and whether it 
is equally abundant on all the successive pairs. 
What is the probable use of this coating ? 

Note the delicate veining of some of the scales as seen through 

the magnifying glass. What does 
this mean? 

Inside the innermost pair are 
found two forked woolly objects; 
what are these ? 

Compare with Figs. 87 and 107. 

Their shape could be more readily 
observed if the woolly coating were 
removed. 

Can you suggest a use for the 
woolly coating? 

Examine a terminal bud in the 
same way in which you have just 
studied the lateral bud. 

Does it contain any parts not 
found in the other? 

What is the appearance of these 
parts ? 

What do they represent ? 

If there is any doubt about their 
nature, study them further on a 
horse-chestnut tree during and im- 
mediately after the process of leaf- 
ing out in the spring. 

For comparison study at least one 
of the following kinds of buds in 
their winter or early spring condi- 
tion : hickory, butternut, beech, ash, magnolia (or tulip tree), lilac, 
balm of Gilead, cottonwood, cultivated cherry.^ 




Fig. 80. — Dissected Bud of Buckeye 
(^sculus macrostachya), showing 
Transitions from Bud-Scales to 



1 Consult the account of the mode of studying buds in Professor W. F. 
Ganong's Teaching Botanist, pp. 208-210. If some of the buds are studied at 
home, pupils will have a better chance to examine at leisure the unfolding 
process. 



BUDS 



121 



132. Nature of Bud-Scales. — The 
fact that the bud-scales are in certain 
cases merely imperfectly developed 
leaves or leaf-stalks is often clearly 
manifest from the series of steps con- 
necting the bud-scale on the one hand 
with the young leaf on the other, which 
may be found in many opening buds, 
as illustrated by Fig. 80. In other 
buds the scales are not imperfect leaves, 
but the little appendages [stipules^ Figs. 
98, 99) which occur at the bases of 
leaves. This kind of bud-scale is 
especially well shown in the magnolia 
and the tulip tree. 

133. Naked Buds. —All of the buds 
above mentioned are winter buds, capa- 
ble of living through the colder months 
of the year, and are scaly buds. 

In the herbs of temperate climates, 
and even in shrubs and trees of tropical 
regions, the buds are often naked, that 
is, nearly or quite destitute of scaly 
coverings (Fig. 81). 

Make a study of the naked buds of any 
convenient herb, such as one of the common 
" geraniums " (Pelargonium), and record what 
you find in it. 

134. Position of Buds. — The dis- 
tinction between lateral and terminal 
buds has already been alluded to. 



Fig. 81. — Tip of Branch 
of Allanthus in Winter 
Condition, showing 
very Large Leaf-Scars 
and nearly Naked Buds. 



122 



FOUNDATIONS OF BOTANY 



The plumule is the first terminal bud which the plant 
produces. Lateral buds are usually axillary^ as shown in 
Fig. 82, that is, they grow in the angle formed by the 
leaf with the stem (Latin axilla, armpit). But not infre- 
quently there are several buds grouped in some way about 




Fig. 82. — Alternate Leaves of Cultivated Cherry, with Buds in 
their Axils, in October. 

a single leaf-axil, either one above the other, as in the 
butternut (Fig. 84), or grouped side by side, as in the red 
maple, the cherry, and the box-elder (Fig. 83). 

In these cases all the buds except the axillary one are 
called accessory or supernumerary buds. 

135. Leaf-Buds and Flower-Buds ; the Bud an Undevel- 
oped Branch. — Such buds as the student has so far 



BUDS 



123 



examined for himself are not large enough to show in the 
most obyious way the relation of the parts and their real 
nature. 

Fortunately, it is easy to obtain a gigantic terminal bud 
which illustrates perfectly the structure and arrangement 
of the parts of buds in 
general. 

Examine and sketch a rather 
small, firm cabbage, preferably 
a red one, which has been split 
lengthwise through the center ^ 
and note 

(a) The short, thick, conical 
stem. 

(b) The crowded leaves 
which arise from the stem, the 
lower and outer ones largest 
and most mature, the upper 
and innermost ones the small- 
est of the series. 

(c) The axillary buds, found 
in the angles made by some 
leaves with the stem. 

Compare the section of the cabbage with Fig 




A ' 

Fig. 83. —Accessory Buds of Box-Elder 
{Negundo). (Magnified.) 

A, front view of group. 

B, two groups seen in profile. 



Most of the buds so far considered were leaf-buds^ that 
is, the parts inside of the scales would develop into leaves, 
and their central axes into stems ; but some were mixed 
buds, that is, they contained both leaves and flowers in an 
undeveloped condition. 

Flower-buds contain the rudiments of flowers only. 

Sometimes, as in the black walnut and the butternut, 
the leaf-buds and flower-buds are readily distinguishable 

1 Half of a cabbage will be enough for the entire division. 



124 



FOUNDATIONS OE BOTANY 



by their difference in form, while in other cases, as in the 
cultivated cherry, the difference in form is but slight. 
The rings of scars about the twig, shown in Figs. 82 
and 85, mark the place where the bases 
of bud-scales were attached. A little 
examination of the part of the twig 
which lies outside of this ring, as shown 
in Fig. 82, will lead one to the conclu- 
sion that this portion has all grown in 
the one spring and summer since the 
bud-scales of that particular ring dropped 
off. Following out this suggestion, it is 
easy to reckon the age of any moder- 
ately old portion of a branch, since it is 
equal to the number of segments between 
the rings. In rapidly growing shoots of 
willow, poplar, and similar trees, 5 or 10 
feet of the length may be the growth of 
a single year, while in the lateral twigs 
of the hickory, apple, or cherry the yearly 
increase may be but a fraction of an inch. 
Such fruiting '•'• spurs " as are shown in 
Fig. 85 are of little use in the permanent 
growth of the tree, and poplars, elms, 
soft maples and other trees shed the 
oldest of these every year. Whatever 
the amount of this growth, it is but the 
lengthening out and development of the 
bud, which may be regarded as an undeveloped stem or 
branch, with its internodes so shortened that successive 
leaves seem almost to spring from the same point. 



I 



Fig. 84. — Accessory- 
Buds of Butternut. 
(Eeduced.) 

I, leaf-scar ; ax, axil- 
lary bud ; a, a', ac- 
cessory buds ; t, 
terminal bud. 



BUDS 



125 



136. Vernation. — Procure a considerable number of buds which 
are just about to burst, and others which have begun to open. Cut 
each across with a razor or very sharp scalpel ; examine first with 
the magnifying glass, and then with the lowest power of the micro- 
scope. Pick to pieces other buds of the same 
kinds under the magnifying glass, and report 
upon the manner in which the leaves are 
packed away. 

The arrangement of leaves in the 
bud is called vernation; some of the 
principal modes are shown in Fig. 86. 




ax 




Fig. 85. — A slowly grown Twig 
of Cherry, 3 inches long and 
about ten years old. 

The pointed bud I is a leaf-bud ; 
the more obtuse accessory 
buds /, / are flower-buds. 



Fig. 86. 

-B, a twig of European elm ; A, a longitudi- 
nal section of the buds of B (considerably 
magnified) ; ax, the axis of the bud, which 
will elongate into a shoot ; sc, leaf -scars. 



In the cherry the two halves of the leaf are folded 
together flat, with the under surfaces outward ; in the 
walnut the separate leaflets^ or parts of the leaf, are folded 



126 



EOUNDATIONS OF BOTANY 



flat and then grouped into a sort of cone ; in the snow- 
ball each half of the leaf is plaited in a somewhat fan-like 
manner, and the edges of the two halves are then brought 
round so as to meet; in the lady's mantle the fan-like 
plaiting is very distinct ; in the wood , sorrel each leaflet 




Fig. 87, 1. — Types of Vernation. 
1, 2, Cherry ; 3, 4, European walnut ; 5, 6, snowball ; 7, lady's mantle ; 8, oxalis. 

is folded smoothly, and then the three leaflets packed 
closely side by side. All these modes of vernation and 
many others have received accurate descriptive names hj 
which they are known to botanists. 

137. Importance of Vernation. — The significance of ver- 
nation is best understood by considering that there are two 



BUDS 



127 



important purposes to be served ; the leaves must be 
stowed as closely as possible in the bud, and upon begin- 
ning to open they must be protected from too great heat 
and dryness until they have reached a certain degree of 
firmness. It may be inferred from Fig. 87, I, that it is 
common for very young leaves to stand vertically. This 
protects them considerably from the scorching effect of the 
sun at the hottest part of the day. Many young leaves, 
as, for instance, those of the silver-leafed poplar, the pear, 
the beech, and the mountain ash, are sheltered and pro- 




FlG. 87, II. 



B C 

Development of an Oxalis Leaf. 



A, full-groAvn leaf ; B, rudimentary leaf, the leaflets not yet evident ; C, moi'e 
advanced stage, the leaflets appearing ; D, a still more advanced stage ; 
B, C, and D, considerably magnified. 



tected from the attacks of small insects by a coating of 
wool or down, which they afterwards lose. Those of the 
tulip tree are enclosed for a little time in thin pouches, 
which serve as bud-scales, and thus entirely shielded from 
direct contact with the outside air (see Sect. 117). 

138. Dormant Buds. — Generally some of the buds on a 
branch remain undeveloped in the spring, when the other 
buds are beginning to grow, and this inactive condition 
may last for many seasons. Finally the bud may die, or 
some injury to the tree may destroy so many other buds 
as to leave the dormant ones an extra supply of food, and 



128 FOUNDATIONS OF BOTANY 

this, with other causes, may force them to develop and to 
grow into branches. 

Sometimes the tree altogether fails to produce buds at 
places wbere they would regularly occur. In the lilac the 
terminal bud usually fails to appear, and the result is con- 
stant forking of the branches. 

139. Adventitious Buds. — Buds which occur in irregu- 
lar places, that is, not terminal nor in or near the axils of 
leaves, are called adventitious buds ; they may spring from 
the roots, as in the silver-leafed poplar, or from the sides 
of the trunk, as in our American elm. In many trees, for 
instance willows and maples, they are sure to appear after 
the trees have been cut back. Willows are thus cut back 
or 'pollarded^ as shown in Plate II, in order to cause them 
to produce a large crop of slender twigs suitable for 
basket-making. 

Leaves rarely produce buds, but a few kinds do so when 
they are injured. Those of the bryophyllum, a plant allied 
to the garden live-for-ever, when they are removed from 
the plant while they are still green and fresh, almost always 
send out buds from the margin. These do not appear at 
random but are borne at the notches in the leaf-margin and 
are accompanied almost from the first by minute roots. 

Pin up a bryophyllum leaf on the wall of the room or 
lay it on the surface of moist earth, and follow, day by day, 
the formation and development of the buds which it may 
produce. 

This plant seems to rely largely upon leaf-budding to 
reproduce itself, for in a moderately cool climate it rarely 
flowers or seeds, but drops its living leaves freely, and from 
each such leaf one or several new plants may be produced. 




Plate II. — Pollarded Willows 



BUDS 
140. Review Summary of Chapter VIII. 
Coverings 



Buds<; 



Contents . 



leaf-buds 
flower-buds 
mixed buds 



129 



Classes of buds as re- 
gards position . . 



regular 
irregular 



Make a sketch of Fig. 82 as it looked in June of the same sum- 
mer ; also as it would look the following June. Sketch the twigs of 
Fig. 30 and Fig. 86 as seen one year later. 



CHAPTER IX 
LEAVES 

141. The Elm Leaf. — Sketch the leafy twig of elm that is sup- 
plied to you.i 

Report on the following points : 

(a) How many rows of leaves ? 

(6) How much overlapping of leaves when the twig is held with 
the upper sides of the leaves toward you? Can you suggest a reason 
for this ? Are the spaces between the edges of the leaves large or 
small compared with the leaves themselves ? 

Pull off a single leaf and make a very careful sketch of its under 
surface, about natural size. Label the broad expanded part the Made, 
and the stalk by which it is attached to the twig, leaf-stalk or petiole. 

Study the outline of the leaf and answer these questions : 

(a) What is the shape of the leaf taken as a whole ? (See Fig. 
88.) Is the leaf bilaterally symmetrical, i.e., is there a middle line 
running through it lengthwise, along which it could be so folded 
that the two sides would precisely coincide ? 

(b) What is the shape of the tip of the leaf? (See Fig. 89.) 

(c) Shape of the base of the leaf? (See Fig. 90.) 

(d) Outline of the margin of the leaf? (See Fig. 93.) 

I^otice that the leaf is traversed lengthwise by a strong midrib 
and that many so-called veins run from this to the margin. Are 

1 Any elm will answer the purpose. Young strong shoots which extend 
horizontally are best, since in these leaves are most fully developed and their 
distribution along the twig appears most clearly. Other good kinds of leaves 
with which to begin the study, if elm leaves are not available, are those of 
beech, oak, willow, peach, cherry, apple. Most of the statements and direc- 
tions above given would apply to any of the leaves just enumerated. If this 
chapter is reached too early in the season to admit of suitable material being 
procured for the study of leaf arrangement, that topic may be omitted until 
the leaves of forest trees have sufficiently matured. 

130 



LEAVES 



131 




Fig. 88, — General Outline of Leaves. 

a, linear; 6, lanceolate ; c, wedge-shaped ; d, spatulate ; e, ovate ; /, obovate 
g, kidney-shaped ; h, orbicular ; i, elliptical. 




e f 9 hi 

Fig. 89. — Tips of Leaves. 

a, acuminate or taper-pointed ; h, acute ; c, obtuse ; d, truncate ; e, retuse ; /, 
emarginate or notched ; g (end leaflet), obcordate ; h, cuspidate, — the point 
sharp andrigid ; i, mucronate, — the point merely a prolongation of the midrib. 



132 



EOUNDATIONS OF BOTANY 




Fig. 90. — Shapes of Bases of Leaves 



1, heart-shaped (uusymmetrically) ; 2, arrow- 
shaped ; 3, halberd-shaped. 



Fig. 91. —Peltate Leaf of 
Tropaeolum. 






Fig. 92. 

A, runclnate leaf of dandelion ; B, 
lyrate leaf. 



/"V^^ 2, 

Fig. 93. — Shapes of Margins 
of Leaves. 
a (1), finely serrate ; (2), coarsely 
serrate; (3), doubly serrate. 
b (1), finely dentate ; (2) , sinuate 
dentate ; (3), doubly dentate. 
c, deeply sinuate, d, wavy. 
e (1), orenate or scalloped ; (2), 
doubly crenate. 



LEAVES 



133 



these veins parallel ? Hold the leaf up towards the light and see 
how the main veins are connected by smaller veinlets. Examine 
with your glass the leaf as held to the light 
and make a careful sketch of portions of 
one or two veins and the intersecting vein- 
lets. How is the course of the veins shown 
on the upper surface of the leaf ? 

Examine both surfaces of the leaf with 
the glass and look for hairs distributed on 
the surfaces. Describe the manner in which 
the hairs are arranged. 

The various forms of leaves are 
classed and described by botanists with 
great minuteness,^ not simply for the 
study of leaves themselves, but also 
because in classifying and describing 
plants the characteristic forms of the 
leaves of many kinds of plants form 
a very simple 




Fig. 94.— Netted Vein- 
ing (pinnate) in tlie 
Leaf of tlie Foxglove. 



and ready 
means of distinguishing them 
from each other and identifying 
them. The student is not ex- 
pected to learn the names of the 
several shapes of leaves as a 
whole or of their bases, tips, or 
margins, except in those cases 
in which he needs to use and 
apply them. 

Many of the words used to describe the shapes of leaves 
are equally applicable to the leaf-like parts of flowers. 




Fig. 95.— Netted Veining (pal- 
mate) in Leaf of Melon. 



1 See Kerner and Oliver's Natural History of Plants, Vol. I, pp. 623-637. 



134 



FOUNDATIONS OE BOTANY 



142. The Maple Leaf. — Sketch the leafy twig. 
Are the leaves arranged in rows like those of the elm ? How are 
they arranged ? 

How are the petioles distorted from their natural positions to 
bring the proper surface of the leaf upward toward the light ? 

Do the edges of these leaves show larger spaces between them 
than the elm leaves did, i.e., would a spray of maple intercept the 
sunlight more or less perfectly than a spray of 
elm ? Pull off a single leaf and sketch its lower 
surface, about natural size. 

Of the two main parts whose names have 
already been learned (blade and petiole), which 
is more developed in the maple than in the 
elm leaf? 
Describe : 

(a) The shape of the maple leaf as a whole. 
To settle this, place the leaf on paper, mark the 
positions of the extreme points and connect 
these by a smooth line. 

(&) Its outline as to main divisions: of what 
kind and how many. 

(c) The detailed outline of the margin 
(Fig. 93). 

Compare the mode of veining or venation of 

the elm and the maple leaf by making a 

diagram of each. 

These leaves agree in being netted-veined ; i.e., in having veinlets 

that join each other at many angles, so as to form a sort of delicate 

lace-work, like Figs. 94 and 95. 

They differ, however, in the arrangement of the principal veins. Such 

a leaf as that of the elm is said to be feather-veined, or pinnately veined. 

The maple leaf, or any leaf with closely similar venation, is said to 

be palmately veined. Describe the difference between the two plans 

of venation. 




Fig. 96.— Piiinately 
Divided Leaf of 
Celandine. 

The blade of the leaf is 
discontinuous, con- 
sisting of several por- 
tions between which 
are spaces in which 
one part of the blade 
has been developed. 



143. Relation of Venation to Shape of Leaves. — As soon 
as the student begins to observe leaves somewhat widely, 



LEAVES 



135 



he can hardly fail to notice that there is a general relation 
between the plan of venation and the shape of the leaf. 
How may this relation be stated? In most cases the 
principal veins follow at the outset a pretty straight 
course, a fact for which the student ought to be able to 
give a reason after he has performed Exp. XXXII. 

On the whole, the arrangement of the 

veins seems to be 

Mf,^ \ •, "V, such as to stiff- 

V '^'vi.: ' . \ en the leal 

most in the 

parts that need 





Fig. 97. — Palmately Divided 
Leaf of Buttercup. 



Fig. 98.— Leaf of Ap- 
ple, with Stipules. 



Fig. 99. — Leaf of 
Pansy, with Leaf- 
Like Stipules. 



most support, and to reach the region near the margin by 
as short a course as possible from the end of the petiole. 

144. Stipules. — Although they are absent from many 
leaves, and disappear early from others, stipules form a 
part of what the botanist regards as an ideal or model 
leaf .1 When present they are sometimes found as little 

1 Unless the elm twigs used in the previous study were cut soon after the 
unfolding of the leaves in spring, the stipules may not have been left in any 
recognizable shape. 



136 



FOUNDATIONS OF BOTANY 




Fig. 100. — Parallel- 
Veined Leaf of Sol- 
omon's Seal. 



bristle-shaped objects at the base of the leaf, as in the 
apple leaf (Fig. 98), sometimes as leaf -like bodies, for 
example in the pansy (Fig. 99), and in 
many other forms, one of which is that 
of spinous appendages, as shown in the 
common locust (Fig. 103). 

145. Parallel -Veined Leaves. — The 
leaves of many great groups of plants, 
such as the lilies, the sedges, and the 
grasses, are commonly parallel-veined^ 
that is, with the veins running nearly 
parallel, lengthwise through the blade, 
as shown in Fig. 100, or 
with parallel veins pro- 
ceeding from a midrib and thence extend- 
ing to the margin, as shown in Fig. 101. 
146. Occurrence of Netted Veining and 
of Parallel Veining. — The student has 
already, in his experiments on germina- 
tion, had an opportunity to observe the 
difference in mode of veining between 
the leaves of some dicotyledonous plants 
and those of monocotyledonous plants. 
This difference is general throughout 
these great groups of flowering plants. 
What is the difference? 

The polycotyledonous pines, spruces, fig. loi. - Parallel 
and other coniferous trees have leaves veinrrunning^f^om 
with but a single vein, or two or three "^^^ib to margin. 
parallel ones, but in their case the veining could hardly 
be other than parallel, since the needle-like leaves are so 




LEAVES 



137 



a% 



narrow that no veins of any considerable length could 
exist except in a position lengthwise of the leaf. 

The fact that a certain plan of venation is found mainly 
in plants with a particular mode of germination, of stem 
structure, and of arrangement of floral parts, is but one 
of the frequent 
cases in botany 
in which the 
structures of 
plants are corre- 
lated in a way 
which it is not 
easy to explain. 

No one knows 
why plants with 
two cotyledons 
should have 
n e 1 1 e d-v e i n e d 
leaves, but many 
such facts as this 
are familiar to 
every botanist. 

147. Simple 
and Compound 
Leaves. — The 
leaves so far studied are simple leaves, that is, leaves of which 
the blades are more or less entirely united into one piece. 
But while in the elm the margin is cut in only a little 
way, in some maples it is deeply cut in toward the bases 
of the veins. In some leaves the gaps between the 
adjacent portions extend all the way down to the petiole 




Fig. 102. — The Fall of the Horse-Chestnut Leaf. 



138 



FOUNDATIONS OF BOTANY 



(in palmately veined leaves) or to the midrib (in pinnately 
veined ones). Such divided leaves are shown in Figs. 
96 and 97. 

In still other leaves, known as compound leaves, the 
petiole, as shown in Fig. 102 (^palmately compound), or the 
midrib, as shown in Fig. 103 {pin- 
nately compound), bears what look to 
be separate leaves. These differ in 
their nature and 
mode of origin 
from the portions 
of the blade of a 
divided leaf. One 
result of this dif- 
ference appears in 
the fact that some 
time before the 
whole leaf is ready 
to fall from the 
tree or other plant 
in autumn, the 
separate portions 
or leaflets of a 
compound leaf are 
seen to be jointed 
at their attach- 
ments, just as whole leaves are to the part of the stem from 
which they grow. In Fig. 102 the horse-chestnut leaf is 
shown at the time of falling, with some of the leaflets 
already disjointed. 

That a compound leaf, in spite of the joints of the 




Fig. 103. — Pinnately Com- 
pound Leaf of Locust, 
with Spines for Stipules. 



Fig. 104.— Pinnately 
Compound Leaf of 
Pea. A tendril takes 
the place of a terminal 
leaflet. 



LEAVES 139 

separate leaflets, is really only one leaf is shown : (1) by 
the absence of buds in the axils of leaflets (see Fig. 82) ; 

(2) by the arrangement of the blades of the leaflets hori- 
zontally, without any twist in their individual leaf-stalks ; 

(3) by the fact that their arrangement on the midrib does 
not follow any of the systems of leaf arrangement on the 
stem (Sect. 149). If each leaflet of a compound leaf should 
itself become compound, the result would be to produce 
a twice compound leaf. Fig. 113 shows that of an acacia. 
What would be the appearance of a thrice compound leaf? 



148. Review Summary of Leaves. ^ 
Parts of a model leaf 

Classes of netted-veined leaves 

Classes of parallel-veined leaves 

Relation of venation to number of cotyledons .... 



Compound leaves ; — types, dependent on arrangement of 11. 
leaflets 



1. 
o 

1 3". 

fl. 
2. 

1. 
2. 



Once, twice, or three times compound .... 
1 Illustrate by sketches if possible. 



CHAPTER X 

LEAF ARRANGEMENT FOR EXPOSURE TO SUN AND AIR; 
MOVEMENTS OF LEAVES AND SHOOTS 



149. Leaf Arrangement.^ — As has been learned from 
the study of the leafy twigs examined, leaves are quite 

generally arranged so as to 
secure the best possible ex- 
posure to the sun and air. 
This, in the vertical shoots 
of the elm, the oak (Fig. 105), 
the apple, beech, and other 
alternate-leaved trees, is not 
inconsistent with their spiral 
arrangement of the leaves 

Fig. 105. — Leaf Arrangement 
of the Oak. 

around the stem. In horizon- 
tal twigs and branches of the 
elm, the beech (Fig. 106), 
the chestnut, the linden, and 
many other trees and shrubs, 
the desired effect is secured 
by the arrangement of all the 
leaves in two flat rows, one on each side of the twig. 





Fig. 106. — Leaf Arrangement of 
European Beech. 



1 See Kerner and Oliver's Natural History of Plants, Vol. I, pp. 396-424. 

140 









^^Ss^B 






r 



Plate III. — Exposure to Sunlight, Japanese Ivy 



LEAT EXPOSUEE TO SUN AND AIR 



141 




Fig. 107. ■ 



■Leaf Arrangement of Horse-Chestnut on 
Vertical Shoots (top view). 



The rows are produced, as it is easy to see on examining 
such a leafy twig, by a twisting about of the petioles. 

The adjustment 
in many opposite- 
leaved trees and 
shrubs consists in 
having each pair 
of leaves cover 
the spaces be- 
tween the pair 
below it, and 
sometimes in the 
lengthening of 
the low^er petioles 
so as to bring 
the blades of 
the lower leaves outside those of the upper leaves. Ex- 
amination of Figs. 107 and 108 will make the matter 
clear. .^^^^ 

The student ^^^— ' ^ 

should not fail to 
study the leafage 
of several trees of 
different kinds on 
the growing tree 
itself, and in 
climbers on walls 
(Plate III), and to 
notice how circum- 
stances modify the position of the leaves. Maple leaves, for 
example, on the ends of the branches are arranged much 




Fig. 108.— Leaf Arrangement of Horse-Chestnut 
on Vertical Shoots (side view). 



142 



rOUKDATIONS OF BOTANY 



like those of the horse-chestnut, but they are found to be 
arranged more nearly flatwise along the inner portions 
of the branches, that is, the portions nearer the tree. 
Figs. 109 and 110 show the remarkable difference in 
arrangement in different branches of the Deutzia, and 
equally interesting modifications may be found in 
alternate-leaved trees, such as the elm and the cherry. 




Fig. 109. — Opposite Leaves of Deutzia i (from tlie same slirub as Fig. 110), as 
arranged on a Horizontal Branch. 



150. Leaf -Mosaics. — In very many cases the leaves at. 
the end of a shoot are so arranged as to form a pretty 
symmetrical pattern, as in the horse-chestnut (Fig. 107). 
When this is sufficiently regular, usually with the space 
between the leaves a good deal smaller than the areas of 
the leaves themselves, it is called a leaf-mosaie (Fig. 111). 
Many of the most interesting leaf-groups of this sort (as 

1 Deutzia crenata. 



LEAF EXPOSURE TO SUN AND AIE 



143 




Fig. 110. — Opposite Leaves of Deutzia, as 
• arranged on a Vertical Branch. 



in the figure above mentioned) are found in the so-called 
root-leaves of plants. Good examples of these are the 

dandelion, chicory, fall 
dandelion, thistle, hawk- 
weed, pyrola, plantain. 
How are the leaves of 
these plants kept from 
shading each other? 

151. Much-Divided 
Leaves. — Not infre- 
quently leaves are cut 
into slender fringe - like 
divisions, as in the carrot, 
tansy, southernwood, 
wormwood, yarrow, dog- 
fennel, cypress-vine, and many other common plants. This 
kind of leaf seems to be adapted to offer considerable 
surface to the sun without cut- 
ting off too much light from 
other leaves underneath. Such 
a leaf is in much less danger of 
being torn by severe winds than 
are broader ones with undivided 
margins. The same purposes 
are served by compound leaves 
with very many small leaflets, 
such as those of the honey- 
locust, mimosa acacia (Fig. 113), 
and other trees and shrubs of the pea family. What kind 
of shade is produced by a horse-chestnut or a maple tree 
compared with that of a honey-locust or an acacia ? 




Fig. 111. 



— Leaf -Mosaic of a 
Campanula. 



144 



rOUNDATIONS OF BOTAirr 




Fig. 112. — A Leaf of Eed Clover. 

At tlie left, leaf by day ; at the right, the same 

leaf asleep at night. 



152. Daily Movements of Leaves. — Many compound 
leaves have the power of changing the position of their 
leaflets to accommodate themselves to varying conditions 
of light and temperature. Some plants have the power 
of directing the leaves or leaflets edgewise towards the 
sun during the hottest parts of the day, allowing them to 

extend their surfaces 
more nearly in a hori- 
zontal direction during 
the cooler hours. 

The so-called "sleep" 
of plants has long been 
known, but this subject 
has been most carefully 
studied rather recelitly. 
The wood sorrel, or oxalis, the common bean, clovers, 
and the locust tree are some of the most familiar of 
the plants whose leaves assume decidedly different posi- 
tions at night from those which they occupy during the 
day. Sometimes the leaflets rise at night, and in many 
instances they droop, as in the red clover (Fig. 112) and 
the acacia (Fig. 113). One useful purpose, at any rate, 
that is served by the leafs taking the nocturnal position is 
protection from frost. It has been proved experimentally 
that when part of the leaves on a plant are prevented from 
assuming the folded position, while others are allowed to 
do so, and the plant is then exposed during a frosty night, 
the folded ones may escape while the others are killed. 
Since many plants in tropical climates fold their leaves 
at night, it is certain that this movement has other pur- 
poses than protection from frost, and probably there is 



LEAP EXPOSURE TO SUN AND AIR 



146 



much yet to be learned about the meaning and importance 
of leaf-movements. 

153. Cause of Sleep-Movements. — The student may- 
very naturally inquire whether the change to the noc- 
turnal position is brought about by the change from light 
to darkness or whether it depends rather upon the time 
of day. It will be interesting to try an experiment in 
regard to this. 

EXPERIMENT XXYI 

Remove a pot containing an oxalis from a sunny window to a 
dark closet, at about the same temperature, and note at intervals of 
five minutes the condition of its leaves for half an hour or more. 




^•^^"^^ 




Fig, 113. — a Leaf of Acacia. 
A, as seen by day ; B, the same leaf asleep at night. 



154. Structure of the Parts which cause Leaf -Motions. — 

In a great number of cases the daily movements of leaves 
are produced by special organs at the bases of the leaf- 
stalks. These cushion-like organs, called pulvini (Fig. 
114), are composed mainly of parenchymatous tissue 



146 



FOUNDATIONS OF BOTANY 



(Sect. 106), which contains much water. It is impossible 
fully to explain in simple language the way in which the 
cells of the pulvini act, but in a general way it may be 
said that changes in the light to which the plant is exposed 
cause rather prompt changes in the amount of water in 

the cells in one portion or 
other of the pulvinus. If the 
cells on one side are filled 
fuller of water than usual, 
that side of the pulvinus will 
be expanded and make the 
leaf-stalk bend toward the 
opposite side. The prompt- 
ness of these 
movements is no 
doubt in consid- 
erable measure 
due to the fact 
that in the pul- 
vini (as in many 
other parts of 
plants) the protoplasm of adjacent cells is connected. 
Delicate threads of protoplasm extend through the cell- 
walls, making the whole tissue a living web, so that any 
suitable stimulus or excitant which acts on one part of 
the organ will soon affect the whole organ. 

155. Vertically Placed Leaves. — Very many leaves, like 
those of the iris (Fig. 44), always keep their principal sur- 
faces nearly vertical, thus receiving the morning and even- 
ing sun upon their faces, and the noonday sun (which is 
so intense as to injure them when received full on the 




Fig. 114. — Compound Leaf of Bean with 
Pulvinus. (The pulvinus shows as an 
enlargement, in the figure about three- 
eighths inch long, at the base of the 
petiole.) 



LEAE EXPOSURE TO SU:tf AND AIR 



147 



surface) upon their edges. This adjustment is most per- 
fect in the compass-plant of the prairies of the Mississippi 
basin. Its leaves stand very nearly upright, many with 





i\ 



ifP 



Fig. 115. — Leaves standing nearly Vertical in Compass-Plant {Silphium laciniatum). 
A, vie-w from east or west ; B, from north or south. 



their edges just about north and south (Fig. 115), so that 
the rays of the midsummer sun will, during every bright 



148 FOUNDATIONS OF BOTANY 

day, strike the leaf-surfaces nearly at right angles during 
a considerable portion of the forenoon and afternoon, 
while at midday only the edge of each leaf is exposed 
to the sun. 

156. Movements of Leaves and Stems toward or away 
from Light (Heliotropic Movements). — The student doubt- 
less learned from his experiments with seedling plants 
that their stems tend to seek light. The whole plant 
above ground usually bends toward the quarter from which 
the strongest light comes. Such movements are called 
heliotropic from two Greek words which mean turning 
toward the sun. How do the plants in a window behave 
with reference to the light ? 

EXPERIMENT XXVH 

How do Young Shoots of English Ivy bend with Reference to Light ? 

— Place a thrifty potted plant of English ivy before a small window, 
e.g., an ordinary cellar window, or in a large covered box, painted dull 
black within and open only on the side toward a south window. 
After some weeks note the position of the tips of the shoots. 
Explain the use of their movements to the plant. 

157. Positive and Negative Heliotropic Movements ; how 
produced. — Plants may bend either toward or away from 
the strongest light. In the former case they are said to 
show positive heliotropism^ in the latter negative heliotro- 
pism. In both cases the movement is produced by unequal 
growth, brought about by the unequal lighting of different 
sides of the stem. If the less strongly lighted side grows 
faster, what kind of heliotropism results? If the more 
strongly lighted side grows faster, what kind of heliotro- 
pism results ? How-would a plant behave if placed on a 



LEAF EXPOSURE TO SUN AND AIR 149 

revolving table before a window and slowly turned during 
the hours of daylight? 

158. Review Summary of Chapter X. 

^ „ , f For vertical twigs .... 

Leaf arrangement ... ^ ^ ^ . , , , . 

I For horizontal twigs . . • 

r Apparatus for 

Movements of leaves . . ■{ Causes of 






Compass-plants .... 
Heliotropic bending of stems 



Uses of 



J Positive . 
\ Negative 



CHAPTER XI 

MINUTE STRUCTURE OF LEAVES; FUNCTIONS OF 
LEAVES 

159. Leaf of Lily. — A good kind of leaf with which 
to begin the study of the microscopical structure of leaves 
in general is that of the lily.-^ 

160. Cross-Section of Lily Leaf. — The student should first exam- 
ine with the microscope a cross-section of the leaf, that is, a very 
thin slice, taken at right angles to the upper and under surfaces and 
to the veins. This will show : 

(a) The upper epidermis of the leaf, a thin, nearly transparent 
membrane. 

(&) The intermediate tissues. 

(c) The lower epidermis. 

Use a power of from 100 to 200 diameters. In order to ascertain 
the relations of the parts, and to get their names, consult Fig. 116. 
Your section is by no means exactly like the figm^e ; sketch it. Label 
properly all the parts shown- in your sketch. 

Are any differences noticeable between the upper and the lower 
epidermis? Between the layers of cells immediately adjacent to 
each? 

161. Under Surface of Lily Leaf. — Examine with a power of 200 
or more diameters the outer surface of a piece of epidermis from the 
lower side of the leaf.^ Sketch carefully, comparing your sketch 
with Figs. 117 and 118, and labeling it to agree with those figures. 

Examine another piece from the upper surface ; sketch it. 
How does the number of stomata in the two cases compare ? 

1 Any kind of lily will answer. 

2 The epidermis may be started with a sharp knife, then peeled off with 
small forceps, and mounted in water for microscopical examination. 

150 



MINUTE STRUCTURE OE LEAVES 



151 



Take measurements from the last three sketches with a scale and, 
knowing what magnifying power was used, answer these questions ^ : 
(a) How thick is the epidermis ? 

(6) What is the length and the breadth of the epidermal cells ? 
(c) What is the average size of the pulp-cells ? 



A stoma is a microscopic pore or slit in the epidermis. 
It is bounded and opened and shut by guard-cells (Fig. 
118, ^), usually two in number. These are generally 




Fig. 116. — Vertical Section of the Leaf of the Beet. (Much magnified.) 

e, epidermis ; p, palisade-cells (and similar elongated cells) ; r, cells filled with 
red cell sap ; i, intercellular spaces ; a, air spaces communicating with the 
stomata ; st, stomata, or breathing pores. 

1 The teacher may measure the size with the camera lucida. 



152 



rOUNDATIONS OF BOTANY 



p— 



P- 



somewhat kidney-shaped and become more or less curved 
as they are fuller or less full of water (see Sect. 170). 

162. Calculation of Number of Stomata per Unit of Area. 
— In order to get a fairly exact idea of the number of 
stomata on a unit of leaf-surface, the most convenient 

plan is to make 
use of a photo- 
micrograph. The 
bromide enlarge- 
ment No. 12 of 
the Tower series 
represents about 
a twenty-five- 
hundredth of a 
square inch of the 
lower epidermis of 
the cyclamen leaf, 
magnified until it 
is about fifteen 
inches square. 
Count the number 
of stomata on the 
entire photograph, 
then calculate the 
number of stomata 
on a square inch 
of the surface of 





Pig. 117. —Epidermis of Leaf of Althaea. 
(Mucli magnified.) 
A, from upper surface ; B, from lower surface. 
^, star-shaped compound hairs ; st, stomata ; p, 
upper ends of palisade-cells, seen through the 
epidermis ; e, cells of epidermis. 



this leaf. If a cyclamen plant has twelve leaves, each 
with an average area of six square inches, calculate the 
number of stomata of the lower epidermis of all the leaves 
taken together. 



MINUTE STRUCTURE OF LEAVES 



153 



cu 



In the case of an apple tree, where the epidermis of the 
lower surface of the leaf contains about 24,000 stomata to 
the square inch, or the black walnut, with nearly 300,000 
to the square inch, 
the total number 
on a tree is incon- 
ceivably large. 

163. Uses of the 
Parts examined. — 
It will be most con- 
venient to discuss 
the uses of the 
parts of the leaf a 
little later, but it 
will make matters 
simpler to state at 
once that the epi- 
dermis serves as a 
mechanical protec- 
tion to the parts 
beneath and pre- 
vents excessive 
evaporation, that 
the palisade-cells 
(which it may not be easy to make out very clearly in a 
roughly prepared section) hold large quantities of the green 
coloring matter of the leaf in a position where it can 
receive enough but not too much sunlight, and the cells 
of the spongy parenchyma share the work of the palisade- 
cells, besides evaporating much water. The stomata 
admit air to the interior of the leaf (where the air spaces 




Fig. 118. —A stoma of Thyme. (Greatly magnified.) 

A, section at right angles to surface of leaf ; B, sur- 
face view of stoma, cu, cuticle ; g, guard-cells*, 
s, stoma ; e, epidermal cells ; a, air chamber ; 
c, cells of spongy parenchyma with grains of 
chlorophyll. 



154 



FOUNDATIONS OF BOTANY 



serve to store and to distribute it), they allow oxygen 
and carbonic acid gas to escape, and, above all, they regu- 
late the evaporation of water from the plant. 

164. Leaf of "India-Rubber Plant." ^ — Study with the micro- 
scope, as the lily leaf was studied, make the same set of sketches, 
note the differences in structure between the two leaves, and try to 
discover their meaning. 

How does the epidermis of the two leaves compare ? 

Which has the larger stomata ? 

Which would better withstand great heat and long drought ? 

165. Chlorophyll as found in the Leaf. — Slice off a 
little of the epidermis from some such soft, pulpy leaf as 




Fig. 119. — Section through Lower Epidermis of Leaf of India-Kubber Plant 
(Ficus elastica). (Magnified 330 diameters.) 
0, opening of pit ; p, pit leading to stoma ; s, stoma, with two guard-cells ; w, 
water-storage cells of epidermis ; a, an air space ; around and above the air 
spaces are cells of the spongy parenchyma. 

that of the common field sorrel,^ live-f or-ever, or spinach ; 
scrape from the exposed portion a very little of the green 
pulp ; examine with the highest power attainable with 
your nucroscope, and sketch several cells. 

1 Ficus elastica, a kind of fig tree. 

2 Rumex Acetosella. 



MINUTE STRUCTUKE OE LEAVES 



155 



Notice that the green coloring matter is not uniformly 
-distributed, but that it is collected into little particles 
called chlorophyll bodies (Fig. 120, p). 

166. Woody Tissue in Leaves. — The veins of leaves 
consist of fibro-vascular bundles containing wood and 
vessels much . like those of the stem 
of the plant. Indeed, these bundles 
in the leaf are continuous with those 
of the stem, and consist merely of 
portions of the latter, looking 
as if unraveled, which pass ; 
outward and upward from the 
stem into the leaf under 
the name of leaf-traces. 
These traverse the peti- 
ole often in a somewhat 
irregular fashion. 




Fig. 120. — Termination 
of a Vein in a Leaf. 
(Magnified about 345 
diameters.) 

V, spirally thickened cells 
of the vein ; p, paren- 
chyma-cells of the 
spongy interior of the 
leaf, with chlorophyll 
bodies; to, nucleated 
cells. 



EXPERIMENT XXVIII 

Passage of Water from 
Stem to Leaf. — Place a 
freshly cut leafy shoot of some 
plant with large thin leaves, 
such as Hydrangea hortensia, 
in eosin solution for a few 
minutes. As soon as the leaves show a decided reddening, pull 
some of them off and sketch the red stains on the scars thus made. 
What does this show? 

167. Experimental Study of Functions of Leaves. — The 

most interesting and profitable way in which to find out 
what work leaves do for the plant is by experimenting 
upon them. Much that relates to the uses of leaves is 



156 FOUNDATIONS OF BOTANY 

not readily shown in ordinary class-room experiments, but 
some things can readily be demonstrated in the experi- 
ments which follow. 

EXPERIMENT XXIX 

Transpiration. — Take two twigs or leafy shoots of any thin-leafed 
plant ; ^ cover the cut end of each stem with a bit of grafting wax^ 
to prevent evaporation from the cut surface. Put one shoot into a 
fruit jar, screw the top on, and leave in a warm room; put the other 
beside it, and allow both to remain some hours. Examine the 
relative appearance of the two, as regards wilting, at the end of the 
time. 

Which shoot has lost most ? Why ? Has the one in the fruit 
jar lost any water ? To answer this question, put the jar (without 
opening it) into a refrigerator ; or, if the weather is cold, put it out 
of doors for a few minutes, and examine the appearance of the inside 
of the jar. What does this show ? ^ 

168. Uses of the Epidermis.* — The epidermis, by its 
toughness, tends to prevent mechanical injuries to the 
leaf, and after the filling up of a part of its outer por- 
tion with a corky substance it greatly diminishes the loss of 
water from the general surface. This process of becom- 
ing filled with cork substance, suherin (or a substance 
of similar properties known as cutin) is essential to the 
safety of leaves or of young stems which have to with- 
stand heat and dryness. The corky or cutinized cell- 
wall is waterproof, while ordinary cellulose allows water 

1 Hydrangea, squash, melon, or cucumber is best; many other kinds will 
answer very well. 

2 Grafting wax may be bought of nurserymen or seedsmen. 

8 If the student is in doubt whether the jar filled with ordinary air might 
not behave in the same way, the question may be readily answered by putting 
a sealed jar of air into the refrigerator. 

* See Kerner and Oliver's Natural History of Plants^ Vol. I, pp. 273-362. 



MINUTE STRUCTURE OF LEAVES 



157 



to soak through it with ease. Merely examining sections 
of the various kinds of epidermis will not give nearly 
as good an idea of their properties as can be obtained 
by studying the behavior during severe droughts of 
plants which have strongly cutinized surfaces and of 
those which have not. Fig. 121, however, may convey 
some notion of the difference between the two kinds of 
structure. In most 
cases, as in the india- 
rubber tree, the ex- 
ternal epidermal cells 
(and often two or 
three layers of cells 
beneath these) are 
filled with water, and 
thus serve as reser- 
voirs from which the 
outer parts of the leaf 
and the stem are at 
times supplied. 

In many cases, noticeably in the cabbage, the epidermis 
is covered with a waxy coating, which doubtless increases 
the power of the leaf to retain needed moisture, and 
which certainly prevents rain or dew from covering the 
leaf -surf aces, especially the lower surfaces, so as to hinder 
the operation of the stomata. Many common plants, like 
the meadow rue and the nasturtium, possess this power 
to shed water to such a degree that the under surface of 
the leaf is hardly wet at all when immersed in water. 
The air-bubbles on such leaves give them a silvery 
appearance when held under water. 




Fig. 121. — Unequal Development of Cuticle 
by Epiderrais-Cells. 
A, epidermis of Butcher's Broom (Hiiscus) ; B, 
epidermis of sunflower ; c, cuticle ; e, epi- 
dermis-cells. 



158 FOUNDATIONS OE BOTANY 

169. Hairs on Leaves. — Many kinds of leaves are more 
or less hairy or downy, as those of the mullein, the 
"mullein pink," many cinquefoils, and other common 
plants. In some instances this hairiness may be a protec- 
tion against snails or other small leaf-eating animals, but 
in other cases it seems to be pretty clear that the woolli- 
ness (so often confined to the under surface) is to lessen 
the loss of water through the stomata. The Labrador 
tea is an excellent example of a plant, with a densely 
woolly coating on the lower surface of the leaf. The 
leaves, too, are partly rolled up (see Fig. 224) ^ with the 
upper surface outward, so as to give the lower surface 
a sort of deeply grooved form, and on the lower surface 
all of the stomata are placed. This plant, like some 
others with the same characteristics, ranges far north into 
regions where the temperature, even during summer, 
often falls so low that absorption of water by the roots 
ceases, since it has been shown that this nearly stops a 
little above the freezing point of water (see Exp. XYII). 
Exposed to cold, dry winds, the plant would then often 
be killed by complete drying if it were not for the pro- 
tection afforded by the woolly, channeled under surfaces 
of the leaves.^ 

170. Operation of the Stomata. — The stomata serve to 
admit air to the interior of the leaf, and to allow moisture, 
in the form of vapor, to pass out of it. They do this not 
in a passive way, as so many mere holes in the epidermis 
might, but to a considerable extent they regulate the 
rapidity of transpiration, opening more widely in damp 
weather and closing in dry weather. The opening is 

1 This adaptation is sufiadently interesting for class study. 




Plate IV. — A Cypress Swamp 



FUNCTIONS OF LEAVES 159 

caused by each of the guard-cells bending into a more 
kidnej^-like form than usual, and the closing by a straight- 
ening out of the guard-cells. The under side of the leaf, 
free from palisade-cells, abounding in intercellular spaces, 
and pretty well protected from becoming covered with 
rain or dew, is especially adapted for the working of the 
stomata, and accordingly we usually find them in much 
greater numbers on the lower surface. On the other 
hand, the little flowerless plants known as liverworts, 
which lie prostrate on the ground, have their stomata on 
the upper surface, and so do the leaves of pond lilies, 
which lie flat on the water. In those leaves which stand 
with their edges nearly vertical, the stomata are dis- 
tributed somewhat equally on both surfaces. Stomata 
occur in the epidermis of young stems, being replaced 
later by the lenticels. Those plants which, like the 
cacti, have no ordinary leaves, transpire through the 
stomata scattered over their general surfaces. 

The health of the plant depends largely on the proper 
working condition of the stomata, and one reason why 
plants in cities often fail to thrive is that the stomata 
become choked with dust and soot. In some plants, as 
the oleander, provision is made for the exclusion of dust 
by a fringe of hairs about the opening of each stoma. If 
the stomata were to become filled with water, their activ- 
ity would cease until they were freed from it; hence 
many plants have their leaves, especially the under sur- 
faces, protected by a coating of wax which sheds water. 

171. Measurement of Transpiration. — We have already 
proved that water is lost by the leaves, but it is worth 
while to perform a careful experiment to reduce our 



160 



FOUNDATIONS OF BOTANY 



knowledge to an exact form, to learn how much water 
a given plant transpires under certain conditions. It is 
also desirable to find out whether different kinds of plants 
transpire alike, and what changes in the temperature, the 
dampness of the air, the brightness of the light, to which 
a plant is exposed, have to do with its transpiration. 
Another experiment will show whether both sides of a 
leaf transpire alike. 



EXPERIMENT XXX 

Amount of Water lost by Transpiration. — Procure a thrifty hydran- 
gea ^ and a small " india-rubber plant," 2 each growing in a small 

, ..^^ flower-pot, and with the number 

of square inches of leaf-surface 
in the two plants not too widely 
different. Calculate the area of 
the leaf-surface for each plant, 
by dividing the surface of a piece 
of tracing cloth into a series of 
squares one-half inch on a side, 
holding an average leaf of each 
plant against this and counting 
the number of squares and parts 
of squares covered by the leaf. 
Or weigh a square inch of tinfoil 
on a very delicate balance, cut 
out a piece of the same kind of 
tinfoil of the size of an average 
leaf, weigh this and calculate the 
leaf-area from the two weights. 
This area, multiplied by the number of leaves for each plant, wiU 
give approximately the total evaporating surface for each. 

Transfer each plant to a glass battery jar of suitable size. Cover 




Fig. 122. — A Hydrangea potted in a 
Battery Jar for Exp. XXX. 



1 The common species of the greenhouses, Hydrangea Hortensia. 

2 This is really a fig, Ficus elastica. 



FUNCTIONS OF LEAVES 161 

j 
the jar with a piece of sheet lead, slit to admit the stem of the plant, | 
invert the jar and seal the lead to the glass with a hot mixture of | 
beeswax and rosin. Seal up the slit and the opening about the ! 
stem with grafting wax. A thistle-tube, such as is used by chem- 
ists, is also to be inserted, as shown in Fig. 122. ^ The mouth of this 
may be kept corked when the tube is not in use for watering. 

Water each plant moderately and weigh the plants separately on ; 
a balance that is sensitive to one-fifth gram. Record the weights, ; 
allow the plants to stand in a sunny, warm room for twenty-four | 
hours and re weigh. 

Add to each plant just the amount of water which is lost,^ and 
continue the experiment in the same manner for several days so as 
to ascertain, if possible, the effect upon transpiration of varying 
amounts of water in the atmosphere. 

Calculate the average loss per 100 square inches of leaf -sui'f ace for i 
each plant throughout the whole course of the experiment. Divide i 
the greater loss by the lesser to find their ratio. Find the ratio of ! 
each plant's greatest loss per day to its least loss per day, and by | 
comparing these ratios decide which transpires more regularly. j 

Try the effect of supplying very little water to each, so that the | 
hydrangea will begin to droop, and see whether this changes the ' 
relative amount of transpiration for the two plants. Vary the con- 
ditions of the experiment for a day or two as regards temperature, I 
and again for a day or two as regards light, and note the effect upon | 
the amount of transpiration. 

The structure of the fig (India-rubber plant) leaf has already been j 
studied. That of the hydrangea is looser in texture and more like I 
the leaf of the lily or the beet (Fig. 116). 

What light does the structure throw on the results of the pre- 
. ceding experiment ? 

.1 

1 It will be much more convenient to tie the hydrangea if one has been ! 
chosen that has but a single main stem. Instead of the hydrangea, the com- j 
mon cineraria, Senecio cruentus, does very well. ; 

2 The addition of known amounts of water may be made most conveniently i 
by measuring it in a cylindrical graduate. j 



162 FOUNDATIONS OF BOTANY 



EXPERIMENT XXXI 

Through which Side of a Leaf of the India-Rubber Plant does Tran- 
spiration occur ? — The student may already have found (Sect. 164) 
that there are no stomata on the upper surface of the fig leaf which 
he studied. That fact makes this leaf an excellent one by means of 
which to study the relation of stomata to transpiration. 

Take two large, sound rubber-plant leaves, cut off pretty close to 
the stem of the plant. Slip over the cut end of the petiole of each 
leaf a piece of small rubber tubing, wire this on, leaving about half 
of it free, then double the free end over and wire tightly, so as to 
make the covering moisture-proof. Warm some vaseline or grafting 
wax until it is almost liquid, and spread a thin layer of it smoothly 
over the upper surface of one leaf and the lower surface of the other. 
Hang both up in a sunny place in the laboratory and watch them for 
a month or more. 

What difference in the appearance of the two leaves becomes 
evident ? What does the experiment prove ? 

172. Endurance of Drought by Plants. — Plants in a wild 
state have to live under extremely different conditions as 
regards water supply (see Chapter XXIV). Observation 
of growing plants during a long drought will quickly 
show how differently the various species of a region bear 
the hardships due to a scanty supply of moisture. It is 
still easier, however, to subject some plants to an artificial 
drought and watch their condition. 

EXPERIMENT XXXII 

Resistance to Drought. — Procure at least one plant from each of 
these groups : 

Group I. Melon-cactus (Echinocactus or Mamillaria), prickly 
pear cactus. 

Group 11. Aloe, Cotyledon (often called Echeveria), houseleek. 



FUNCTIONS OF LEAVES 163 

Group III. Live-for-ever (Sedum Telephium'), Bryophyllum, English 
ivy, " ivy-leafed geranium," (Pelargonium peltatum), or any of the 
fleshy-leafed begonias. 

Group TV. Hydrangea (H. Hortensia), squash or cucamber, sun- 
flower. 

The plants should be growing in pots and well rooted. Water 
them well and then put them all in a warm, sunny place. Note the. 
appearance of all the plants at the end of twenty-four houi\s. If any 
are wilting badly, water them. Keep on with the experiment, in no 
case watering any plant or set of plants until it has wilted a good 
deal. Record the observations in such a way as to show just how 
long a time it took each plant to begin to wilt from the time when 
the experiment began. If any hold out more than a month, they 
may afterwards be examined at intervals of a week, to save the time 
required for daily observations. If possible, account by the struc- 
ture of the plants for some of the differences observed. Try to learn 
the native country of each plant used and the soil or exposure natural 
to it. 

173. Course traversed by Water through the Leaf. — The 

same plan that was adopted to trace the course of water in 
the stem (Exp. XXI) may be followed to discover its path 
through the leaf. 

EXPERIMENT XXXIII 

Rise of Sap in Leaves. — Put the freshly cut ends of the petioles 
of several thin leaves of different kinds into small glasses, each con- 
taining eosin solution to the depth of one-quarter inch or more. 
Allow them to stand for half an hour, and examine them by holding 
up to the light and looking through them to see into what parts the 
eosin solution has risen. Allow some of the leaves to remain as 
much as twelve hours, and examine them again. The red-stained 
portions of the leaf mark the lines along which, under natural con- 
ditions, sap rises into it. Cut across (near the petiole or midrib 
ends) all the principal veins of some kind of large, thin leaf. Then 
cut off the petiole and at once stand the cut end, to which the blade 



164 FOUNDATIONS OF BOTANY 

is attached, in eosin solution. Repeat with another leaf and stand 
in water. What do the results teach ? 

174. Total Amount of Transpiration. — In order to pre- 
vent wilting, the rise of sap during the life of the leaf 
must have kept pace with the evaporation from its sur- 
face. The total amount of water that travels through the 
roots, stems, and leaves of most seed-plants during their 
lifetime is large, relative to the weight of the plant itself. 
During 173 days of growth a corn-plant has been found to 
give off nearly 31 pounds of water. During 140 days of 
growth a sunflower-plant gave off about 145 pounds. A 
grass-plant has been found to give off its own weight of 
water every twenty-four hours in hot, dry summer weather. 
This would make about 6 1- tons per acre every twenty-four 
hours for an ordinary grass-field, or rather over 2200 pounds 
of water from a field 50 X 150 feet, that is, not larger than 
a good-sized city lot. Calculations based on observations 
made by the Austrian forest experiment stations showed 
that a birch tree with 200,000 leaves, standing in open 
ground, transpired on hot summer days from 700 to 900 
pounds, while at other times the amount of transpiration 
was probably not more than 18 to 20 pounds.^ 

These large amounts of water are absorbed, carried 
through the tissues of the plant, and then given off by the 
leaves because the plant-food contained in the soil-water 
i« in a condition so diluted that great quantities of water 
must be taken in order to secure enough of the mineral 
and other substances which the plant demands from the 
soil. Active transpiration may also have other causes. 

1 See B. E. Fernow's discussion in Report of Division of Forestry of U. S. 
Department of Agriculture, 1889. 



FUNCTIONS OF LEAVES 165 

Meadow hay contains about two per cent of potash, or 
2000 parts m 100,000, while the soil- water of a good soil 
does not contain more than one-half part in 100,000 parts. 
It would therefore take 4000 tons of such water to furnish 
the potash for one ton of hay. The water which the 
root-hairs take up must, however, contain far more potash 
than is assumed in the calculation above given, so that the 
amount of water actually used in the growth of a ton of 
hay cannot be much more than 260 tons.^ 

175. Accumulation of Mineral Matter in the Leaf. — Just 
as a deposit of salt is found in the bottom of a seaside pool 
of salt water which has been dried up by the sun, so old 
leaves are found to be loaded with mineral matter, left 
behind as the sap drawn up from the roots is evaporated 
through the stomata. A bonfire of leaves makes a sur- 
prisingly large heap of ashes. An abundant constituent 
of the ashes of burnt leaves is silica, a substance chemic- 
ally the same as sand. This the plant is forced to absorb 
along with the potash, compounds of phosphorus, and other 
useful substances contained in the soil-water; but since 
the silica is of hardly any value to most plants, it often 
accumulates in the leaf as so much refuse. Lime is much 
more useful to the plant than silica, but a far larger quan- 
tity of it is absorbed than is needed; hence it, too, accu- 
mulates in the leaf. 

176. Nutrition, Metabolism.^ — The manufacture of the 
more complex plant-foods, starch, sugar, and so on, from 

1 See the article, " Water as a Factor in th.e Growth of Plants," by B. T. 
Galloway and Albert F. Woods, Year-Book of U. S. Department of Agriculture, 
1894. 

2 See Kerner and Oliver's Natural History of Plants, Vol. I, pp. 371^83. 
Also Pfeffer's Physiology of Plants, translated by Ewart, Chapter VIII. 



166 FOUNDATIONS OF BOTANY 

the raw materials which are afforded by the earth and air 
and all the steps of the processes hj which these foods are 
used in the life and growth of the plant are together known 
as its nutrition. When we think more of the chemical 
side of nutrition than of its relation to plant-life, we call 
any of the changes or all of them metabolism, which means 
simply chemical transformation hi living tissues. There 
are two main classes of metabolism — the constructive kind, 
which embraces those changes which build up more com- 
plicated substances out of simpler ones (Sect. 179), and the 
destructive kind, the reverse of the former (Sect. 184). A 
good many references to cases of plant metabolism have 
been made in earlier chapters, but the subject comes up in 
more detail in connection with the study of the work of leaves 
than anywhere else, because the feeding which the ordinary 
seed-plant does is very largely done in and by its leaves. 

177. Details of the Work of the Leaf. — A leaf has four 
functions to perform: (1) Starch-making; (2) assimila- 
tion ; ^ (3) excretion of water ; (4) respiration. 

178. Absorption of Carbon Dioxide and Removal of its 
Carbon. — Carbon dioxide is a constant ingredient of the 
atmosphere, usually occurring in the proportion of about 
four parts in every 10,000 of air or one twenty-fifth of one 
per cent. It is a colorless gas, a compound of two simple 
substances or elements, carbon and oxygen, the former 
familiar to us in the forms of charcoal and graphite, the 
latter occurring as the active constituent of air. 

1 lu many works on Botany (1) and (2) are both compounded under the 
term assimilation. Many botanists (most of the American ones) apply the 
name photosynthesis or photosyntax to the starch-making process, but these 
names are not wholly satisfactory, and perhaps it is as well (as suggested by 
Professor Atkinson) to name the process from its result. 



FUNCTIONS OE LEAVES 167 

Carbon dioxide is produced in immense quantities by 
the decay of vegetable and animal matter, by the respira- 
tion of animals, and by all fires in which wood, coal, gas, 
or petroleum is bui'ned. 

Green leaves and the green parts of plants, when they 
contain a suitable amount of potassium salts, have the 
power of removing carbon dioxide from the air (or in 
the case of some aquatic plants from water in which it is 
dissolved), retaining its carbon and setting free part or all 
of the oxygen. This process is an important part of the 
work done by the plant in making over raw materials into 
food from which it forms its own substance, 

EXPERIMENT XXXIV 

Oxygen-Making in Sunlight. — Place a green aquatic plant in a 
glass jar full of ice-cold fresh water, in front of a sunny window.^ 
Place a thermometer in the jar, watch the rise of temperature, and 
note at what point you first observe the formation of oxygen bub- 
bles. Remove to a dark closet for a few minutes and examine by 
lamplight, to see whether the rise of bubbles stiU continues. 

This gas may be shown to be oxygen by collecting some 
of it in a small inverted test-tube filled with water and 
thrusting the glowing coal of a match just blown out into 
the gas. It is not, however, very easy to do this satisfac- 
torily before the class. 

Repeat the experiment, using water which has been well boiled 
and then quickly cooled. Boiling removes all the dissolved gases 
from water, and they are not re-dissolved in any considerable quantity 
for many hours. 

1 Elodea, Myriophyllum, Chrysosplenium, Potamogeton, Fontinalis, any of 
the green aquatic flowering plants, or even the common confervaceous plants, 
known a.s pond-scum or "frog-spit," will do for this experiment. 



168 FOUNDATIONS OF BOTANY 

Ordinary air, containing a known per cent of carbon dioxide, 
if passed very slowly over the foliage of a plant covered with a bell- 
gl'ass and placed in full sunlight, will, if tested chemically, on com- 
ing out of the bell-glass be found to have lost a little of its carbon 
dioxide. The pot in which the plant grows must be covered with a 
lid, closely sealed on, to prevent air charged with carbon dioxide (as 
the air of the soil is apt to be) from rising into the bell-glass. 

179. Disposition made of the Absorbed Carbon Dioxide. 

— It would lead the student too far into the chemistry of 
botany to ask him to follow out in detail the changes by 
which carbon dioxide lets go part at least of its oxygen 
and gives its remaining portions, namely, the carbon, and 
perhaps part of its oxygen, to build up the substance of 
the plant. Starch is composed of three elements : hydro- 
gen (a colorless, inflammable gas, the lightest of known 
substances), carbon, and oxygen. Water is composed 
largely of hydrogen, and, therefore, carbon dioxide and 
water contain all the elements necessary for making starch. 
The chemist cannot put these elements together to form 
starch, but the plant can do it, and at suitable temperatures 
starch-making goes on constantly in the green parts of 
plants when exposed to sunlight and supplied with water 
and carbon dioxide.^ The seat of the manufacture is in 
the chlorophyll bodies, and protoplasm is without doubt the 
manufacturer, but the process is not understood by chemists 
or botanists. No carbon dioxide can be taken up and used 
by plants growing in the dark, nor in an atmosphere con- 
taining only carbon dioxide, even in the light. 

1 Very likely the plant makes sugar first of all and then rapidly changes 
this into starch. However that may be, the first kind of food made in the 
leaf and retained long enough to be found there by ordinary tests is starch. 
See Pfeffer's Physiology of Plants, translated by Ewart, Vol. I, pp. 317, 318. 




Plate V. — A Saprophyte, Indian Pipe 



FUNCTIONS OF LEAVES 169 

A very good comparison of the leaf to a mill has been 
made as follows ^ : 



The mill : 


Palisade-cells and unde 




cells of the leaf. 


Raw material used : 


Carbon dioxide, water. 


Milling apparatus : 


Chlorophyll grains. 


Energy by which the mill 




is run : 


Sunlight. 


Manufactured product : 


Starch. 


Waste product : 


Oxygen. 



180. Plants Destitute of Chlorophyll not Starch-Makers. 

— Aside from the fact that newly formed starch grains are 
first found in the chlorophyll bodies of the leaf and the 
green layer of the bark, one of the best evidences of 
the intimate relation of chlorophyll to starch-making is 
derived from the fact that plants which contain no chloro- 
phyll cannot make starch from water and carbon dioxide. 
Parasites, like the dodder, which are nearly destitute of 
green coloring matter, cannot do this; neither can sapro- 
phytes or plants which live on decaying or fermenting 
organic matter, animal or vegetable. Most saprophytes, 
like the moulds, toadstools, and yeast, are flowerless plants 
of low organization, but there are a few (such as the 
Indian pipe (Plate V), which flourishes on rotten wood 
or among decaying leaves) that bear flowers and seeds. 

181. Detection of Starch in Leaves. — Starch may be 
found in abundance by microscopical examination of the 
green parts of growing leaves, or its presence may be 
shown by testing the whole leaf with iodine solution. 

1 By Professor George L. Goodale. 



170 



FOUNDATIONS OF BOTANY 



EXPERIMENT XXXy 



Occurrence of Starch in Nasturtium Leaves. — Toward the close of 
a very sunny day collect some bean leaves or leaves of nasturtium 
(Tropceolum). Boil these in water for a few minutes, to kill the 
protoplasmic contents of the cells and to soften and swell the starch 
grains.^ 

Soak the leaves, after boiling, in strong alcohol for a day or two, 
to dissolve out the chlorophyll, which would otherwise make it diffi- 
cult to see the blue color of the starch test, if any were obtained. 
Rinse out the alcohol with plenty of water 
and then place the leaves for ten or fifteen 
minutes in a solution of iodine, rinse off 
with water and note what portions of the 
leaf, if any, show the presence of starch. 

EXPERIMENT XXXYI 

Consumption of Starch in Nasturtium 

(Tropceolum) Leaves. — Select some healthy 
leaves of Tropseolum on a plant growing 
vigorously indoors or, still better, in the 
opeu' air. Shut off the sunlight from 
parts of the selected leaves (which are to 
be left on the plant and as little injured 
as may be) by pinning circular disks of cork on opposite sides of 
the leaf, as shown in Fig. 123. On the afternoon of the next day 
remove these leaves from the plant and treat as described in the 
preceding experiment, taking especial pains to get rid of all the 
chlorophyll by changing the alcohol as many times as may be neces- 
sary. What does this experiment show in regard to the consump- 
tion of starch in the leaf? What has caused its disappearance? 

182. Rate at which Starch is manufactured. — The 

amount of starch made in a day by any given area of 

1 The leaves, collected as above described, may, after boiling, be kept in 
alcohol for winter use. They also make excellent material for the micro- 
scopical study of starch in the leaf. 




Fig. 123. — Leaf of Tropgeo- 
lum partly covered with 
Disks of Cork and ex- 
posed to Sunlight. 



EUNCTIONS OF LEAVES 171 

foliage must depend on the kind of leaves, the tempera- 
ture of the air, the intensity of the sunlight, and some 
other circumstances. Sunflower leaves and pumpkin or 
squash leaves have been found to manufacture starch at 
about the same rate. In a summer day fifteen hours long 
they can make nearly three-quarters of an ounce of starch 
for each square yard of leaf-surface. A full-grown squash 
leaf has an area of about one and one-eighth square feet, 
and a plant may bear as many as 100 leaves. What would 
be the daily starch-making capacity of such a plant ? ^ 

183. Assimilation. — From the starch in the leaf, grape- 
sugar or malt-sugar is readily formed, and some of this in 
turn is apparently combined on the spot with nitrogen, 
sulphur, and phosphorus. These elements are derived 
from nitrates, sulphates, and phosphates, taken up in a 
dissolved condition by the roots of the plant and trans- 
ported to the leaves. The details of the process are not 
understood, but the result of the combination of the 
sugars or similar substances with suitable (very minute) 
proportions of nitrogen, sulphur, and phosphorus is to 
form complex nitrogen compounds. These are not pre- 
cisely of the same composition as the living protoplasm 
of plant-cells or as the reserve proteids stored in seeds 
(Sects. 14, 17), stems (Sect. 127), and other parts of 
plants, but are readily changed into protoplasm or proteid 
foods as necessity may demand. 

■ Assimilation is by no means confined to leaves ; indeed, 
most of it, as above suggested, must take place in other 
parts of the plant. For instance, the manufacture of the 
immense amounts of cellulose, of cork, and of the com- 

1 See PfefEer's Physiology of Plants, translated by Ewart, Vol. I, p. 324. 



172 FOUNDATIONS OF BOTANY 

pound (lignin) characteristic of wood-fiber, that go to make 
up the main bulk of a large tree must be carried on in the 
roots, trunk, and branches of the tree. 

184. Digestive Metabolism. — Plant-food in order to be 
carried to the parts where it is needed must be dissolved, 
and this dissolving often involves a chemical change and 
is somewhat similar to digestion as it occurs in animals. 
The newly made starch in the leaf must be changed to a 
sugar or other substance soluble in water before it can be 
carried to the parts of the plant where it is to be stored 
or to rapidly growing parts where it is to be used for 
building material. On the other hand, starch, oil, and 
such insoluble proteids as are deposited in the outer por- 
tion of the kernel of wheat and other grains are extremely 
well adapted to serve as stored food, but on account of 
their insoluble nature are quite unfit to circulate through 
the tissues of the plant. The various kinds of sugar are 
not well adapted for storage, since they ferment easily in 
the presence of warmth and moisture if yeast-cells or 
suitable kinds of bacteria are present. 

Two important differences between starch-making in 
the green parts of plants and the non-constructive or the 
destructive type of metabolism should be carefully noticed. 
These latter kinds of metabolism go on in the dark as 
well as in the light and do not add to the total weight 
of the plant. 

185. Excretion of V/ater and iRespiration. — Enough has 
been said in Sect. 174 concerning the former of these pro- 
cesses. Respiration^ or breathing in oxygen and giving 
off carbonic acid gas, is an operation which goes on con- 
stantly in plants, as it does in animals, and is necessary to 



FUNCTIONS OF LEAVES 



173 




their life. For, like animals, plants get the energy with 
which they do the work of assimilation, growth, reproduc- 
tion, and performing their movements from the oxidation 
of such combustible substances as oil, starch, and sugar.i 
The amount of oxy- 



gen absorbed and of car- 
bonic acid given off is, 
however, so trifling com- 
pared with the amount 
of each gas passing in 
the opposite direction, 
while starch-making is 
going on in sunlight, 
that under such circum- 
stances it is difficult to 
observe the occurrence 
of respiration. In ordi- 
nary leafy plants the 
leaves (through their 
stomata) are the principal organs for absorption of air, but 
much air passes into the plant through the lenticels of 
the bark. 

In partly submerged aquatics especial provisions are 
found for carrying the air absorbed by the leaves down to 
the submerged parts. This is accomplished in pond lilies 
by ventilating tubes which traverse the leaf-stalks length- 
wise. In many cases such channels run up and down the 
stem (Fig. 124). 

1 The necessity of an air supply about the roots of the plant may be shown 
by filling the pot or jar in which the hydrangea was grown for the transpi- 
ration experiment perfectly full of water and noting the subsequent appear- 
ance of the plant at periods twelve to twenty-four hours apart. 




Fig. 124, — Cross-Section of Stem of Marestail 
{Hippuris) with Air-Passages, a. 



174 



FOUNDATIONS OF BOTANY 



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FUNCTIONS OF LEAVES 175 

187. The Fall of the Leaf. — In the tropics trees retain 
most of their leaves the year round ; a leaf occasionally 
falls, but no considerable portion of them drops at any 
one season.^ The same statement holds true in regard to 
our cone-bearing evergreen trees, such as pines, spruces, 
and the like. But the impossibility of absorbing soil-water 
when the ground is at or near the freezing temperature 
(Exp. XVII) would cause the death, by drying up, of 
trees with broad leaf-surfaces in a northern winter. And 
in countries where there is much snowfall, most broad- 
leafed trees could not escape injury to their branches from 
overloading with snow, except by encountering winter 
storms in as close-reefed a condition as possible. For 
such reasons our common shrubs and forest trees (except 
the cone-bearing, narrow-leafed ones already mentioned) 
are mostly deciduous^ that is they shed their leaves at the 
approach of winter. 

The fall of the leaf is preceded by important changes 
in the contents of its cells. 

EXPERIMENT XXXYII 

Does the Leaf vary in its Starch Contents at Different Seasons ? 

Collect in early summer some leaves of several kinds of trees and 
shrubs and preserve them in alcohol. Collect others as they are 
beginning to drop from the trees in autumn and preserve them in 
the same way. Test some of each lot for starch as described in 
Sect. 181. 

What does the result indicate? 

Much of the sugary and protoplasmic contents of the 
leaf disappears before it falls. These valuable materials 

1 Except where there is a severe dry season. 



176 FOUNDATIONS OE BOTANY | 

1 



have been absorbed by the branches aiid roots, to be used j 
again the following spring. ; 

The separation of the leaf from the twig is accomplished i 
by the formation of a layer of cork cells across the base of \ 
the petiole in such a way that the latter finally breaks off ': 
across the surface of the layer. A waterproof scar is thus ] 
already formed before the removal of the leaf, and there is J 
no waste of sap dripping from the wound where the leaf- ] 
stalk has been removed, and no chance for moulds to j 
attack the bark or wood and cause it to decay. In com- j 
pound leaves each leaflet may become separated from the > 
petiole, as is notably the case with the horse-chestnut leaf j 
(Fig. 102). In woody monocotyledons, such as palms, the ■ 
leaf-stalks do not commonly break squarely off at the base, ' 
but wither and leave projecting stumps on the stem 
(Plate VI). ' 

The brilliant coloration, yellow, scarlet, deep red, and 
purple, of autumn leaves is popularly but wrongly sup- i 
posed to be due to the action of frost. It depends merely [ 
on the changes in the chlorophjdl grains and the liquid 
cell-contents that accompany the withdrawal of the proteid -■ 
material from the tissues of the leaf. The chlorophyll j 
turns into a yellow insoluble substance after the valuable j 
materials which accompany it have been taken away, and : 
the cell sap at the same time may turn red. Frost per- | 
haps hastens the break-up of the chlorophyll, but individual j 
trees often show bright colors long before the first frost, ] 
and in very warm autumns most of the changes in the foli- ; 
age may come about before there has been any frost. j 

188. Tabular Review of Experiments. *; 

[Continue the table from Sect. 128.] j 




Plate VI. — Fan Palms 



FUNCTIONS OF LEAVES 



177 



189. Review Summary of Minute Structure of Leaves. ^ 

General structure, distribution of 

parenchyma, and prosenchyma 
Layers of tissue seen on a cross- , 

section i 

Structure of epidermis . . . *■ 
Structure of stomata .... 
Distribution of stomata . . . 
Structure and distribution of 

chlorophyll bodies .... 



190. Review Summary of Functions of Leaves. 



Principal uses of 



fibro-vascular bundles 
epidermis . 
stomata . . 
air spaces . 
palisade-cells . 
spongy parenchyma 
waxy coating . 
hairs . . 



Substances received by the leaf . . . 

Substances manufactured by the leaf . . 

Substances given off by the leaf . . . 

Mineral substances accumulated in the leaf 
Statistics in regard to transpiration . 
Statistics in regard to starch-making . . 



k; 



om the air 
from the soil 



I into the air 
[ into the stem 



1 Illustrate with sketches and diagrams. 



CHAPTER XII 
PROTOPLASM AND ITS PROPERTIES 

191. The Cell in its Simplest Form. — Sufficient has 
been said in the preceding chapters, and enough tissues 
have been microscopically studied, to make it pretty clear 
what vegetable cells, as they occur in flowering plants, 
are like. In Chapter XI, leaf-cells have been taken for 
granted and their work described in some detail. Before 
going further, it is worth while to consider the structure 
of an individual cell, and to see of what kinds of activity 
it is capable. 

In studying the minute anatomy of bark, wood, pith, 
and other tissues the attention is often directed to the 
cell-wall without much regard to the nature of the cell- 
contents. Yet the cell-wall is not the cell, any more than 
the lobster shell or the crayfish shell is the lobster or the 
crayfish. The contained protoplasm with its nucleus is the 
cell} The cell reduced to its lowest terms need not have 
a cell-wall, but may consist simply of a mass of proto- 
plasm, usually containing a portion of denser consistency 
than the main bulk, known as the nucleus. 

Such cells, without a cell-wall, are not common in the vege- 
table world, but are frequently encountered among animals. 

192. The Slime Moulds.^ — One of the best examples of 
masses of naked protoplasm leading an individual existence 

1 See Kerner and Oliver's Natural History of Plants, Vol. I, pp. 21-51. 

2 Strasburger, Noll, Schenk, and Sehimper's Text-Book of Botany, pp. 50-52 
and 302-305. 

178 



PROTOPLASM A^D ITS PROPERTIES 179 

is found in the slime moulds, which live upon rotten tan 
bark, decaying wood, and so on. These curious organ- 
isms have so many of the characteristics both of animals 
and of plants that they have been described in zoologies 
under the former title and in botanies under the latter 
one. Perhaps it would not really be so absurd a state- 
ment as it might seem, to say that every slime mould leads 
the life of an animal during one period of its existence and 
of a plant at another period. At any rate, whatever their 
true nature, these little masses of unenclosed protoplasm 
illustrate admirably some of the most important properties 
of protoplasm. Slime moulds spring from minute bodies 
called spores (Fig. 125, a) which differ from the seeds of 
seed-plants not only in their microscopic size but still 
more in their lack of an embryo. The spores of slime 
moulds are capable, when kept dry, of preserving for 
many years their power of germination, but in the pres- 
ence of moisture and warmth they will germinate as soon 
as they are scattered. During the process of germination 
the spore swells, as shown at 5, and then bursts, discharging 
its protoplasmic contents, as seen at c and d. This in a 
few minutes lengthens out and produces at one end a hair- 
like eilium, as shown at e,f,.g. These ciliated bodies are 
called swarmspores^ from their power of swimming freely 
about by the vibrating motion of the cilia. Every swarm- 
spore has at its ciliated end a nucleus^ and at the other end 
a bubble-like object which gradually expands, quickly dis- 
appears, and then again expands. This contractile vacuole 
is commonly met with in animalcules, and increases the 
likeness between the slime moulds and many microscopic 
animals. The next change of the swarmspores is into an 



180 



rOUNDATIONS OF BOTANY 



Amoeba form (so called from one of the most interesting and 
simplest of animals, the Amoeba^ found on the surface of 








Fig. 125. — A Slime Mould, (a-m, inclusive, x 540 times, n x 90 times.) 

mud and the leaves of water plants). In this condition, 
as shown at A, ^, ^, the spores creep about over the sur- 
face of the decaying vegetable material on which the 



PROTOPLASM AND ITS PROPERTIES 181 

slime moulds live. Their movement is caused by a thrust- 
ing out of the semi-liquid protoplasm on one side of the 
mass, and a withdrawal of its substance from the other 
side. At length many amoeba-shaped bodies unite, as at Z, 
to form a larger mass, m, which finally increases to the 
protoplasmic network shown at n. This eventually col- 
lects into a roundish or egg-shaped firm body, inside of 
which a new crop of spores is produced. It is not easy to 
trace the manner in which the nourishment of these simple 
plants is taken. Pi'obably they absorb it from the decay- 
ing matter upon which they live during their amoeba-like 
period, and after they have formed the larger masses, n. 
193. Characteristics of Living Protoplasm. ^ — The behav- 
ior of the slime moulds during their growth and transfor- 
mations, as just outlined, affords a fair idea of several of 
the remarkable powers which belong to living protoplasm, 
which have been summed up as follows : 

(1) The power to take up new material into its own 
substance {selective absorption). This is not merely a proc- 
ess of soaking up liquids, such as occurs when dry earth 
or a sponge is moistened. The protoplasmic lining of a 
root-hair, for example, selects from the soil-water some 
substances and rejects others (Sect. 65). 

(2) The ability to change certain substances into others 
of different chemical composition (metabolism, Sect. 176). 
Carbon dioxide and water, losing some oxygen in the 
process, are combined into starch; starcli is changed into 
various kinds of sugar and these back into starch again ; 
starch becomes converted into vegetable acids, into cellu- 
lose, or into oil ; or the elements of starch are combined 

1 See Huxley's Essays, Vol. I, essay on " The Physical Basis of Life." 



182 FOUNDATIONS OF BOTANY 

with nitrogen to m?.ke various proteid compounds, either 
for immediate use or for reserve food. Many other com- 
plicated transformations occur. 

(3) The power to cast off waste or used-up material 
{excretion). Getting rid of surplus water (Sect. 174) and 
of oxygen (Sect. 178) constitutes a very large part of the 
excretory work of plants. 

(4) The capacity for growth and the production of off- 
spring (reproduction). These are especially characteristic 
of living protoplasm. It is true that non-living objects 
may grow in a certain sense, as an icicle or a crystal of 
salt or of alum in a solution of its own material does. 
But growth by the process of taking suitable particles 
into the interior of the growing substance and arranging 
them into an orderly structure (Fig. 126) is possible only 
in the case of live protoplasm. 

(5) The possession of the power of originating move- 
ments not wholly and directly caused by any external 
impulse (automatic movements). Such, for instance, are 
the lashing movements of the cilia of the swarmspores 
of slime moulds, or the slow pendulum movements of 
Oscillatoria (Sect. 269), or the slow vibrating movements 
of the stipules of the "telegraph plant" (Desmodium)^ 
not uncommon in greenhouses. 

(6) The power of shrinking or closing up (contractility). 
This is illustrated by the action of the contractile vacuole 
of the slime moulds and of many animalcules and by all 
the muscular movements of animals. 

(7) Sensitiveness when touched or otherwise disturbed, 
for instance, by a change of light or of temperature 
(irritability). 



PROTOPLASM AND ITS PROPERTIES 



183 



194. Nature and Occurrence of Irritability in Plants.^ — 

Mention has already been made of the fact that certain 
parts of plants respond to suitable stimuli that is exciting 




Fig. 126. —Protoplasm in Ovule and Fruit of Snowberry (Sijmphoricarpus 

racemosus). 

A, cells from ovule, x 340; B, cells from an ovule further developed, x 340 ; C, D, 

cells from pulp of fruit, x no ; n, nucleus ; p, protoplasm ; s, cell-sap. 
In the young and rapidly growing cells, A and B, the cell-sap is not present, or 

present only in small quantities, while in the older cells, C and D, it occupies 

a large portion of the interior of the cell. 

causes. Geotropic movements (Sect. 70) are due to 
the response of roots or shoots to gravitation. These 

1 See Strasburger, Noll, Schenk, and Schimper's Text-Book of Botany, 
pp. 160-162 and 269-274. 



184 



EOUNDATIONS OF BOTANY 



i 



'/y 



movements are due to unequal growth induced in the 
younger portions of the plant by the action of gravi- 
tation upon it. Other movements (of 
ordinary foliage leaves, of the floral leaves 
of many flowers, and of other parts of a 
few flowers) are produced by changes in 
the distention or turgescence of some of the 
cells in the organs which move and have 
nothing to do with growth. The closing 
of the leaves of insect-catching plants is 
briefly described in Sect. 410, and the 
"sleep" of leaves, due to movements of 
the pulvini, was described in Sect. 152. 
A few facts in regard to the opening and 
closing of flowers will be found in 
Sect. 440.' 

The stimuli which cause movements of 
leaves or of the irritable parts of flowers 
are of several kinds. Light is the main 
cause which induces leaves to open from 
their night position to that usual in the 
daytime. In the case of flowers, it is 
sometimes light and sometimes warmth 
which causes them to open. Leaves which 
catch insects may be made to close by 
touching them, but the sensitive- plants, 
of which there are several kinds found in 
the United States, and a much more sensi- 
tive one in tropical America, all fold their leaflets, on 
being touched, into the same position which they assume 
at night. 




Fig. 127. — Stinging 
Hair of Nettle, with 
Nucleus. (Much 
magnified.) The ar- 
rows shoAv the direc- 
tion of the currents 
in the protoplasm. 



PROTOPLASM AND ITS PROPERTIES 185 

195. Circulation of Protoplasm. — When confined by a 
cell-wall, protoplasm often manifests a beautiful and con- 
stant rotating movement, traveling incessantly up one 
side of the cell and down the other.^ A more complicated 
motion is the circulation of protoplasm^ shown in cells of 
the jointed blue hairs in the flower of the common spider- 
wort and in the stinging hairs of the nettle (Fig. 127). 
The thin cell- wall of each hair is lined with a protoplasmic 
layer in which are seen many irregular, thread-like cur- 
rents, marked by the movements of the granules, of which 
the protoplasmic layer is full. 

1 See Huxley and Martiu's Elementary Biology, under Chara. 



CHAPTER XIII 

INFLORESCENCE, OR ARRANGEMENT OF FLOWERS 
ON THE STEM 



196. Regular Positions for Flower-Buds. — Flower-buds, 
like leaf -buds, occur regularly either in the axils of leaves 
or at the end of the stem or branch and are therefore 
either axillary or terminal. 

197. Axillary and Solitary Flowers; Indeterminate 
Inflorescence. — The simplest possible arrangement for 

flowers which arise from the axils of 
leaves is to have a single flower spring 
from each leaf -axil. Fig. 128 shows 
how this plan appears in a plant with 
opposite leaves. As long as the stem 
continues to grow, the production of new 
leaves may be followed by that of new 



:SkM 




Fig. 128. — Axillary and 
Solitary Flowers of 
Pimpernel. 




Fig, 129. — liaceme of 
Common Eed Currant. 
p, peduncle ; p', pedicel 



flowers. Since there is no definite limit to the number 
of flowers which may appear in this way, the mode of 
flowering just described (with many others of the same 
general character) is known as indeterminate inflorescence. 

186 



ARRANGEMENT OF FLOWERS ON THE STEM 187 




Fig. 130. — Simple Umbel of Cherry. 



198. The Racemes and Related Forms. — If the leaves 
along the stem were to become very much dwarfed and the 

flowers brought closer together, 
as they frequently are, a kind 
of flower-cluster like that of the 
currant (Fig. 129) or the lily- 
of-the-valley would result. Such 
an inflorescence is called a ra- 
ceme ; the main flower-stalk is 
known as the 'peduncle ; the little 
individual flower-stalks are pedi- 
cels^ and the small, more or 
less scale -like leaves of the 
peduncle are bracts.^ 
Frequently the lower pedicels of a cluster on the 
general plan of the raceme are longer than the upper 
ones and make a some- 
what flat-topped cluster, 
like that of the hawthorn, 
the sheep laurel, or the 
trumpet creeper. This 
is called a corymb. 

In many cases, for ex- 
ample the parsnip, the 
Sweet Cicely, the gin- 
seng, and the cherry, a 

group of pedicels of fig. ISl. — catkins of WlIlow. 

nearly equal length .J, stamlnate flowers ; 5, pistillate flowers 




1 It is hardly necessary to say that the teacher will find it better in every 
way, if material is abundant, to begin the study of flower-clusters with the 
examination of typical specimens by the class, 



188 FOUNDATIONS OF BOTANY 

spring from about the same point. This produces a 
flower-cluster called the umbel (Fig. 130). 

199. Sessile Flowers and Flower-Clusters. — Often the 
pedicels are wanting, or the flowers are sessile, and then 
a modification of the raceme is produced which is called 
a spike^ like that of the plantain (Fig. 132). The 
willow, alder, birch, poplar, and many other common 
trees bear a short, flexible, rather scaly spike (Fig. 
131), which is called a catkin. 

The peduncle of a spike is often so much short- 
ened as to bring the flowers into a somewhat globu- 
.^^ lar mass. This is called a head (Fig. 132). Around 

the base of the head usually 
occurs a circle of bracts known 
as the involucre. The same 
Qj '^_ "^'^^ name is given to a set of bracts 

^-^ 'Ifr,' which often surround the bases 

y I V . \\ of the pedicels in an umbel. 

200. The Composite Head. — 
The plants of one large group. 
Fig. 132. -Spike of Plantain and ^f which the dandcliou, the 

Head of Red Clover. 

daisy, the thistle, and the sun- 
flower are well-known members, bear their flowers in 
close involucrate heads on a common receptacle. The 
whole cluster looks so much like a single flower that it is 
usually taken for one by non-botanical people. In many 
of the largest and most showy heads, like that of the 
sunflow^er and the daisy, there are two kinds of flowers, 
the ray-flowers^ around the margin, and the tubular disk- 
flowers of the interior of the head (Fig. 133). The early 
botanists supposed the whole flower-cluster to be a single 




ARRANGEMENT OF FLOWERS ON THE STEM 189 




Fig. 133. — Head of Yarrow. 

A, top view. (Magnified.) B, lengthwise section. (Magnified.) ?'e, receptacle ; i, 
involucre; r, ray-flowers; d, disk-flowers; c, corolla; s, stigma; c^, chaff, 
or bracts of receptacle. 



rf.^#t%s» .^. 




9W&. 




Fig. 134. 
Panicle of Oat. 



r 

Fig. 135. — Compound Umbel 
of Carrot. 



190 



FOUNDATIONS OF BOTANY 



compound flower. This belief gave rise to the name of 
one family of plants, Oompositce, that is, plants with com- 
pound flowers. In such heads as those of the thistle, the 
cud weed, and the everlasting there are no ray-flowers, 
and in others, like those of the dandelion and the chicory, 
all the flowers are ray-flowers. 

201. Compound Flower-Clusters. — If the pedicels of a 
raceme branch, they may produce a compound raceme, or 




A BCD 

Fig. 136. — Diagrams of Inflorescence. 
A, panicle ; B, raceme ; C, spike ; E, umbel ; D, head. 

panicle, like that of the oat (Fig. 134).^ Other forms of 
compound racemes have received other names. 

An umbel may become compound by the branching of 
its flower-stalks (Fig. 135), each of which then bears a 
little umbel, an umhellet. 

202. Inflorescence Diagrams. — The plan of inflorescence 
may readily be indicated by diagrams like those of Fig. 136. 

The student should construct such diagrams for some rather com- 
pUcated flower-clustei's, like those of the grape, horse-chestnut or 
buckeye, hardhack, vervain, or many grasses. 

1 Panicles may also be formed by compound cymes (see Sect. 204). 



ARRANGEMENT OF FLOWERS ON THE STEM 191 



i- 



203. Terminal Flowers ; Determinate Inflorescence 

The terminal bud of a stem may be a flower-bud. In this 
case the direct growth of the stem is stopped or deter- 
mined by the appearance of the flower ; hence such plants 
are said to have a determinate inflorescence. The simplest 
possible case of this kind is that 
in which the stem bears but one 
flower at its summit. 

204. The Cyme. — Very often 
flowers appear from lateral (axil- 
lary) buds, below the terminal 
flower, and thus give rise to a 
flower-cluster called a cyme. 
This may have only three flowers, 
and in that case would look very 
much like a three-flowered 
umbel. But in the raceme, 
corymb, and umbel the order of 
flowering is from below upward, 
or from the outside of the clus- 
ter inward, because the lowest or the outermost flowers 
are the oldest, while in determinate forms of inflorescence 
the central flower is the oldest, and therefore the order of 
blossoming is from the center outwards. Cymes are very 
commonly compound, like those of the elder and of many 
plants of the pink family, such as the Sweet William and 
the mouse-ear chickweed (Fig. 137). They may also, as 
already mentioned, be panicled, thus making a cluster 
much like Fig. 136, A. 




Fig. 137. — Compound. Cyme of 

Mouse-Ear Chickweed. 
t, the terminal (oldest) flower. 



CHAPTER XIV 
THE STUDY OF TYPICAL FLOWERS 

(Only one of the three flowers described to be studied by aid of these 
directions.) 

205. The Flower of the Trillium. — Cut off the flower-stalk rather 
close to the flower; stand the latter, face down, on the table, and 
draw the parts then shown. Label the green leaf-like parts sepals, 
and the white parts, which alternate with these, petals. Turn the 
flower face up, and make another sketch, labeling the parts as before, 
together with the yellow enlarged extremities or anthers of the stalked 
organs called stamens. 

Note and describe the way in which the petals alternate with the 
sepals. Observe the arrangement of the edges of the petals toward 
the base, — how many with both edges outside the others, how many 
with both edges inside, how many with one edge in and one out. 

Note the veining of both sepals and petals, more distinct in 
which set?i 

Pull off a sepal and make a sketch of it, natural size ; then remove 
a petal, flatten it out, and sketch it, natural size. 

Observe that the flower-stalk is enlarged slightly at the upper end 
into a rounded portion, the receptacle, on which all the parts of the 
flower rest. 

Note how the six stamens arise from the receptacle and their 
relations to the origins of the petals. Remove the remaining petals 

1 In flowers with delicate white petals the distribution of the libro-vascular 
bundles in these can usually be readily shown by standing the freshly cut end 
of the peduncle in red ink for a short time, until colored veins begin to appear 
in the petals. The experiment succeeds readily with apple, cherry, or plum 
blossoms ; with white gilliflower the coloration is very prompt. Lily-of-the- 
valley is perhaps as interesting a flower as any on which to try the experi- 
ment, since the well-defined stained stripes are separated by portions quite 
free from stain, and the pistils are also colored. 

192 



THE STUDY OF TYPICAL FLOWEKS 193 

(cutting them off near the bottom with a knife), and sketch the sta- 
mens, together with the other object, the pistil^ which stands in the 
center. 

Cut off one stamen, and sketch it as seen through the magnifying 
glass. Notice that it consists of a greenish stalk, the filament, and 
a broader portion, the anther (Fig. 149). The latter is easily seen 
to contain a prolongation of the green filament, nearly surrounded 
by a yellow substance. In the bud it will be found that the anther 
consists of two long pouches or anther-cells, which are attached by 
their whole length to the filament, and face inward (towards the 
center of the flower). When the flower is fairly open, the anther- 
cells have already split down their margins, and are discharging a 
yellow, somewhat sticky powder, the pollen. 

Examine one of the anthers with the microscope, using the two- 
inch objective, and sketch it. 

Cut away all the stamens, and sketch the pistil. It consists of a 
stout lower portion, the ovary, which is six-ridged or angled, and 
which bears at its summit three slender stigmas. 

In another flower, which has begun to wither (and in which the 
ovary is larger than in a newly opened flower), cut the ovary across 
about the middle, and try to make out with the magnifying glass 
the number of chambers or cells which it contains. Examine the 
cross-section with the two-inch objective ; sketch it, and note partic- 
ularly the appearance and mode of attachment of the undeveloped 
seeds or ovules with which it is filled. Make a vertical section of 
another rather matui-e ovary, and examine this in the same way. 

Using a fresh flower, construct a diagram to show the relation of 
the parts on an imaginary cross-section, as illustrated in Fig. 157.^ 
Construct a diagram of a longitudinal section of the flower, on the 
general plan of those in Fig. 155, but showing the contents of the 
ovary. 

Make a tabular list of the parts of the flower, beginning with the 
sepals, giving the order of parts and number in each set. 

1 It is important to notice that sucli a diagram is not a picture of the section 
actually produced by cutting through the flower crosswise at any one level, 
but that it is rather a projection of the sections through the most typical part 
of each of the floral organs. 



194 FOUNDATIONS OF BOTANY 

206. The Flower of the Tulip. i — Make a diagram of a side view 
of the well-opened flower, as it appears when standing in sunlight. 
Observe that there is a set of outer flower-leaves and a set of inner 
ones. 2 Label the outer set sepals and the inner set petals. In most 
flowers the parts of the outer set are greenish, and those of the inner 
set of some other color. It is often convenient to use the name 
perianth, meaning around the flower, for the two sets taken together. 
Note the white waxy bloom on the outer surface of the outer seg- 
ments of the perianth. What is the use of this ? Note the manner 
in which the inner segments of the perianth arise from the top of the 
peduncle and their relation to the points of attachment of the outer 
segments. In a flower not too widely opened, note the relative posi- 
tion of the inner segments of the perianth, how many wholly outside 
the other two, how many wholly inside, how many with one edge in 
and one edge out. 

Remove one of the sepals by cutting it oif close to its attachment 
to the peduncle, and examine the veining by holding it up in a strong 
light and looking through it. Make a sketch to show the general 
outline and the shape of the tip. 

Examine a petal in the same way, and sketch it. 

Cut off the remaining portions of the perianth, leaving about a 
quarter of an inch at the base of each segment. Sketch the upright, 
triangular, pillar-like object in the center, label it pistil, sketch the 
organs which spring from around its base, and label these stamens. 

Note the fact that each stamen arises from a point just above and 
within the base of a segment of the perianth. Each stamen consists 
of a somewhat conical or awl-shaped portion below, the filament^ sur- 
mounted by an ovate linear portion, the anther. Sketch one of the 
stamens about twice natural size and label it x 2. Is the attach- 
ment of the anther to the filament such as to admit of any nodding 
or twisting movement of the former ? In a young flower, note the 
two tubular pouches or anther-cells of which the anther is composed, 
and the slits by which these open. Observe the dark-colored pollen 

1 TuUpa Gesneriana. As the flowers are rather expensive, and their parts 
are large and firm, it is not absolutely necessary to give a flower to each pupil, 
but some may be kept entire for sketching and others dissected by the class. 
All the flowers must be single. 

2 Best seen in a flower which is just opening. 



THE STUDY OF TYPICAL FLOWERS 195 

which escapes from the auther-cells and adheres to paper or to the 
fingers. Examine a newly opened anther with the microscope, using 
the two-inch objective, and sketch it. 

Cut away all the stamens and note the two portions of the pistil, 
a triangular prism, the ovary, and three roughened scroll-like objects 
at the top, the three lobes of the stigma. Make a sketch of these 
parts about twice natural size, and label them x 2. Touch a small 
camel's-hair pencil to one of the anthers, and then transfer the pollen 
thus removed to the stigma. This operation is merely an imitation 
of the work done by insects which visit the flowers out of doors. 
Does the pollen cling readily to the rough stigmatic surface ? Examine 
this adhering pollen with the two-inch objective, and sketch a few 
grains of it, together with the bit of the stigma to which it clings. 
Compare this drawing with Fig. 162. Make a cross-section of the 
ovary about midway of its length, and sketch the section as seen 
through the magnifying glass. Label the three chambers shown 
cells of the ovary ^ or locules, and the white egg-shaped objects within 
ovules.^ 

Make a longitudinal section of another ovary, taking pains to 
secure a good view of the ovules, and sketch as seen through the 
magnifying glass. 

Making use of the information already gained and the cross- 
section of the ovary as sketched, construct a diagram of a cross- 
section of the entire flower on the same general plan as those shown 
in Fig. 157.3 

Split a flower lengthwise,* and construct a longitudinal section of 
the entire flower on the plan of those shown in Fig. 155, but showing 
the contents of the ovary. 

207. The Flower of the Buttercup. — Make a diagram of the 
mature flower as seen in a side view, looking a little down into it. 
Label the pale greenish-yellow, hairy, outermost parts sepals, and 

1 Notice that the word cell here means a comparatively large cavity, and is 
not used in the same sense in which we speak of a wood-cell or a pith-cell. 

2 The section will be more satisfactory if made from an older flower, grown 
out of doors, from which the perianth has fallen. In this case label the con- 
tained objects seeds. 

3 Consult also the footnote on p. 193. 

* One will do for an entire division of the class. 



196 FOUNDATIONS OF BOTANY 

the larger bright yellow parts above and within these petals, and 
the yellow-knobbed parts which occupy a good deal of the interior 
of the flower stamens. 

Note the difference in the position of the sepals of a newly 
opened flower and that of the sepals of a flower which has opened as 
widely as possible. Note the way in which the petals are arranged 
in relation to the sepals. In an opening flower observe the arrange- 
ment of the edges of the petals, how many entirely outside the 
others, how many entirely inside, how many with one edge in and 
the other out. 

Cut off a sepal and a petal, each close to its attachment to the 
flower ; place both, face down, on a sheet of paper, and sketch about 
twice the natural size and label it x 2. Describe the difference in 
appearance between the outer and the inner surface of the sepal and 
of the petal. Note the little scale at the base of the petal, inside. 

Strip off all the parts from a flower which has lost its petals, 
until nothing is left but a slender conical object a little more than 
an eighth of an inch in length. This is the receptacle or summit of 
the peduncle. 

In a fully opened flower, note the numerous yellow-tipped stamens, 
each consisting of a short stalk, the filament, and an enlarged yellow 
knob at the end, the anther. Note the division of the anther into 
two portions, which appear from the outside as parallel ridges, but 
which are really closed tubes, the anther-cells. 

Observe in the interior of the flower the somewhat globular mass 
(in a young flower almost covered by the stamens). This is a group 
of pistils. Study one of these groups in a flower from which the 
stamens have mostly fallen off, and make an enlarged sketch of the 
head of pistils. Remove some of the pistils from a mature head, 
and sketch a single one as seen with the magnifying glass. Label 
the little knob or beak at the upper end of the pistil stigma, and the 
main body of the pistil the ovary. Make a section of one of the 
pistils, parallel to the flattened surfaces, like that shown in Fig. 150, 
and note the partially matured seed within. 



CHAPTER XV 

PLAN AND STRUCTURE OF THE FLOWER AND ITS 
ORGANS 



208. Parts or Organs of the Flower. — Most showy 
flowers consist, like those studied in the preceding chap- 
ter, of four circles or sets of organs, the sepals, petals, 
stamens, and pistils. The sepals, taken together, consti- 
tute the calyx; the petals, taken together, constitute the 
corolla (Fig. 138).i Some- 
times it is convenient to have 
a word to comprise both calyx 
and corolla ; for this the term 
perianth is used. A flower 
which contains all four of 
these sets is said to be com- 
plete. Since the work of the 
flower is to produce seed, and 
seed-forming is due to the 
cooperation of stamens and 
pistils, or, as they are often 
called from their relation to the reproductive organs of 
spore-plants, microsporophylls and macrosporophylls (see 
Sect. 374), these are known as the essential organs 
(Fig. 138). The simplest possible pistil is a dwarfed and 

1 The flower of the waterleaf Hydrophyllum canadense, modified by the 
omission of the hairs on the stamens, is here given because it shows so plainly 
the relation of the parts. 

197 




cor- 



Fia. 138. — The Parts of the Flower. 

cal, calyx ; cor, corolla ; st, 

stamens; p, pistil. 



198 



FOUNDATIONS OF BOTANY 



greatly modified leaf (Sect. 222), adapted into a seed- 
bearing organ. Such a pistil may be one-seeded, as in 
Fig. 166, or several-seeded, as in the diagrammatic one 
(Fig. 150) ; it is called a, carpel. The calyx and corolla are 
also known as the floral envelopes. Flowers which have 
the essential organs are called perfect flowers. They may, 
therefore, be perfect without being complete. Incomplete 
flowers with only one row of parts in the 
perianth are said to be apetalous (Fig. 139). 
209. Regular and Symmetrical Flowers. 
— A flower is regular if all the parts of 
the same set or circle are alike in size and 
shape, as in the stonecrop (Fig. 140). Such 
flowers as that of the violet, the monkshood, 
and the sweet pea (Fig. 141) are irregular. 
Symmetrical flowers are those whose calyx, 
corolla, circle of stamens, and set of 
carpels consist each of the same number of parts, or in 
which the number in every case is a multiple of the 
smallest number found in any set. The stonecrop is 




Fig. 139. — Apetal- 
ous Flower of 
(Eur opeae) Wild 
Ginger. 




Fig. 140. — Flower of Stonecrop. ' 

I, entire flower (magnified) ; II, vertical section (magnified). ; 

I 

symmetrical, since it has five sepals, five petals, ten sta- ' 
mens, and five carpels. Roses, mallows, and mignonette i 



STRUCTURE OF THE FLOWER AND ITS ORGANS 199 



are familiar examples of flowers which are unsymmet- 
rical because they have a large, indefinite number of 
stamens ; the portulaca is unsymmetrical, since it has two 
divisions of the calyx, five or six petals, and seven to 
twenty stamens. 

210. The Receptacle. — The parts of the flower are 
borne on an expansion of the peduncle, called the recep- 
tacle. Usually, as in the flower of the grape (Fig. 250), 
this is only a slight enlargement of the peduncle, but in 




Fig. 141. — Irregular Corolla ot 
Sweet Pea. 

A, side view ; B, front view ; s, stand 
ard ; w w, wings ; k, keel. 




the lotus and the magnolia the receptacle is of great size, 
particularly after the petals have fallen and the seed has 
ripened. The receptacle of the rose (Fig. 142) is hollow, 
and the pistils arise from its interior surface. 

211. Imperfect or Separated Flowers. — The stamens 
and pistils may be produced in separate flowers, which 
are, of course, imperfect. This term does not imply that 
such flowers do their work any less perfectly than others, 
but only that they have not both kinds of essential organs. 
In the very simple imperfect flowers of the willow (Fig. 
143) each flower of the catkin (Fig. 131) consists merely 



200 FOUNDATIONS OF BOTANY 

of a pistil or a group of (usually two) stamens, springing 
from the axil of a small bract. 

Staminate and pistillate flowers may be borne on differ- 
ent plants, as they are in the willow, or they may be 
borne on the same plant, as in the hickory and the hazel, 
among trees, or in the castor-oil plant, Indian corn, and 
the begonias. When staminate and pistillate flowers are 
borne on separate plants, such a plant is said to be 
dicecious, that is, of two households ; when both kinds of 
flower appear on the same individual, the plant is said 
to be mo7ioecious, that is, of one household. 

212. Study of Imperfect Flowers. — Examine, draw, and describe 
the imperfect flowers of some of the following dioecious plants and 
one of the monoecious plants : i 

f early meadow rue. 

Dioecious plants J willow. 

i poplar. 

f walnut, oak, chestnut. 

Monoecious plants <| hickory, alder, beech. 

i birch, hazel, begonia. 

213. Union of Similar Parts of the Perianth. — The 

sepals may appear to join or cohere to form a calyx which 
is -more or less entirely united into one piece, as in Figs. 
139 and 148. In this case the calyx is said to be gamo- 
sepalous, that is, of wedded sepals. In the same way the 
corolla is frequently gamopetalous^ as in Figs. 144-148. 
Frequently the border or limb of the calyx or corolla is 
more or less cut or lobed. In this case the projecting 

1 For figures or descriptions of these or allied flowers consult Gray's 
Manual of Botany, Emerson's Trees and Shrubs of Massachusetts, Newhall's 
?>ees of the Northern United States, or Le Maout and Decaisne's Traite 
General de Botanique. 



STRUCTURE OF THE FLOWER AND ITS ORGANS 201 




portions of the limb are known as divisions, teeth, or 

lobes/ Special names of great use in accurately describing 

plants are given to a large number of forms of 4he gamo- 

petalous corolla. Only a few of these 

names are here given, in connection with 

the figures. 

When the parts of either circle of the 
perianth are wholly unconnected with each 
other, that is, polysepalous or polypetalous, 
such parts are said to be distinct. 

214. Parts of the Stamen and the Pistil. 
— The stamen usually consists of a hollow 
portion, the ayither (Fig. 149, a), borne on a 
stalk called the filament (Fig. 149, /), which 
is often lacking. Inside the anther is a pow- 
dery or pasty substance called pollen or microspores (Sect. 
374). The pistil usually consists of a small chamber, the 
ovary., which contains the ovules., macrospores (Sect. 374), 
or rudimentary seeds, a slen- 
der portion or stalk, called the 
style^ and at the top of this a 
ridge, knob, or point called 
the stigma. These parts are 
all shown in Fig. 150. In 
many pistils the stigma is 
borne directly on the ovary. 
215. Union of Stamens with 
Each Other. — Stamens 



Fig. U2. 
AKose, Longitudi- 
nal Section. 




may 



Fig. 143. — Flowers of Willow. 
(Magnified.) 
be wholly unconnected with a, stamlnate flower ; B, pistillate flower. 

1 It would not be safe to assume that the gamosepalous calyx or the gamo- 
petalous corolla is really formed by the union of separate portions, but it is 
very convenient to speak of it as if it were. 



202 



FOUNDATIONS 0¥ BOTANY 




each other or distinct^ or they may cohere by their fila- 
ments into a single group, when they are said to be 
monadelphous^ of one brotherhood (Fig. 
151), into two groups (diadelphous) (Fig. 
152), or into many groups. In some 
flowers the stamens are held together in 
a ring by their coherent anthers (Fig. 
153). 

216. Union of Pistils. — The pistils 
may be entirely separate from each 
other, distinct and simple, as they are 

Fig. 144.— Bell-Shaped . , , , , ■ 

Corolla of Beii-Fiower m the buttcrcup and the stonecrop, or 

(Campanula). scvcral may join to form one compound 

pistil of more or less united carpels. In the latter case 

the union generally affects the ovaries, but often leaves 

the styles separate, or it may result 

in joining ovaries and styles, but 

leave the stigmas separate or at any 

rate lobed, so as to show of how 

many separate carpels the compound 

pistil is made up. Even when there 

is no external sign to show the 

compound nature of 

the pistil, it can usu- y^^m 



ally be recognized ^t iv 
from the study of L^( '|f 
a cross-section of the 





Fig. 145. — Salver-Shaped 
Corolla of Jasmine. 
(Magnified.) 



Fig. 146. 

Wheel-Shaped Corolla 

of Potato. 



ovary. 

217. Cells of the 
Ovary ; Placentas. — Compound ovaries are very com- 
monly several-celled, that is, they consist of a number of 



STRUCTURE OF THE FLOWER AND ITS ORGANS 203 



separate cells ^ or chambers, more scientifically known 
as locules. Fig. 154, B, shows a three-celled ovary- 
seen in cross-section. The ovules are not borne indis- 
criminately by any part of the lining of the ovary. In 
one-celled pistils they frequently grow in a line running 
along one side of the ovary, as in the pea pod (Fig. 271). 
The ovule-bearing line is called a placenta ; in compound 
pistils there are commonly as many placentas as there are 




Fig. 147.— Tubu- 
lar Corolla, from 
Head of Bache- 
lor's Button. 



Fig. 148. — Labi- 
ate or Ringent 
Corolla of Dead 
Nettle. 



Fig, 149. — Parts of a 
Stamen. 
A, front ; B, back ; a, an- 
ther ; c, connective; 
/, filament. 



Fig. 150. — Parts 
of the Pistil. 

ov, ovary. 
sty, style. 
stig, stigma. 



separate pistils joined to make the compound one. Pla- 
centas on the wall of the ovary, like those in Fig. 154, J., 
are called parietal placentas ; those which occur as at B, 
in the same figure, are said to be central, and those which, 
like the form represented in C of the same figure, consist 
of a column rising from the bottom of the ovary are 
called free central placentas. 

1 Notice that the word cell is here used in an entirely different sense from 
that in which it has been employed in the earlier chapters of this book. As 
applied to the ovary, it means a chamber or compartment. 



204 



FOUNDATIONS OF BOTANY 




Fig. 151. 

Monadelphous 

Stamens of 

Mallow. 



218. Union of Separate Circles. — The members of one 
of the circles of floral organs may join those of another 
circle, thus becoming adnate, adherent, or consolidated. 

In Fig. 139 the calyx tube is adnate to the 
ovary. In this case the parts of the flower do 
not all appear to spring from the receptacle. 
Fig. 155 illustrates three common cases as 
regards insertion of the parts of the flower. 
In I they are all inserted on the receptacle, 
and the corolla and stamens are said to be 
hypogynous, that is, beneath the pistil. In II 
the petals and the stamens appear as if they 
had grown fast to the calyx for some distance, 
so that they surround the pistil, and they are 

therefore said to be perigynous^ that is, 

around the pistil. In III all the parts are 

free or unconsolidated, except the petals 

and stamens ; the stamens may be described 

as epipetalous, that is, growing on the petals. 
Sometimes some or all 
of the other parts stand 
upon the ovary, and such 

Fig. i52.-Diadeipiious parts are said to be epig- 

StamensofSAveetPea. ^^^^^^^ ^j^^^ -^^ ^^^ ^1^^ 

ovary, like the petals and. stamens of the 
white water-lily (Fig. 156). 

219. Floral Diagrams. — Sections (real fig. 153.— stamens 
or imagfinarv) through the flower leng'th- ^^ ^ Thistle, with 

^ J / & i=> Anthers united 

wise, like those of Fig. 155, help greatly into a Ring. 

in givino- an accurate idea of the relative "'^"^*^<^^'^*^^^''^ 5./', 

, , , filaments, bearded 

position of the floral organs. Still more on the sides. 




STRUCTURE OF THE FLOWER AND TIS ORGANS 205 

important in this way are cross-sections, which may be 
recorded in diagrams like those of Fig. 157.^ In con- 
structing such diagrams it 
will often be necessary to 
suppose some of the parts 
of the flower to be laised 
or lowered from their true 
position, so as to bring 
them into such relations 
that all could be cut by a 
single section. This would, for instance, be necessary 
in making a diagram for the cross-section of the flower 




A B' ' C 

Jb'iG. 154. — Principal Types of Placenta. 
A._ parietal placenta ; B, centi'al placenta ; 
C, free central placenta ; A and B, trans- 
verse sections ; C, longitudinal section. 




I II III 

Fig. 155.— Insertion of the 
Floral Organs. 
I, Hypogynous, all the other parts on 
the receptacle, beneath the pistil ; 
II, Perigynous, petals and stamens 
apparently growing out of the calyx , 
around the pistil ; III, corolla 
hypogynous, stamens epipetalous. 



Fig. 156. — White Water-Lily . The 
inner petals and the stamens groov- 
ing from the ovary. 



of the white water-lily, of which a partial view of one 
side is shown in Fig. 156.^ 



1 For floral diagrams see Le Maout and Decaisne's Traite General de 
Botanique, or Eichler's Bliithendiagramme. 

2 It is best to begin practice on floral diagrams with flowers so firm and 
large that actual sections of them may be cut with ease and the relations of 
the parts in the section readily made out. The tulip is admirably adapted 
for this purpose. 



206 



FOUNDATIONS OF BOTANY 



Construct diagrams of the longitudinal section and the 

transverse section of several large flowers, following the 

method indicated in Figs. 155 and 157, but making 

• the longitudinal section show 

the interior of the ovary.^ It 

is found convenient to distin- 





I II 

Fig. 157. — Diagram of Cross-Sections of Flowers. 

I, columbine ; II, heath family ; III, iris family. In each diagram the dot along- 
side the main portion indicates a cross-section of the stem of the plant. In 
II every other stamen is more lightly shaded, because some plants of the 
heath family have five and some ten stamens. 

guish the sepals from the petals by representing the 
former with midribs. The diagrammatic symbol for a 
stamen stands for a cross-section of the anther, and that 
for the pistil is a section of the ovary. If any part is 
lacking in the flower (as in the case of flowers which 
have some antherless filaments) the missing or abortive 
organ may be indicated by a dot. In the diagram of the 
Iris Family (Fig. 157, III) the three dots inside the flower 
indicate the position of a second circle of stamens, found 
in most flowers of monocotyledons but not found in this 
family. 

1 Among the many excellent early flowers for this purpose may be men- 
tioned trillium, hloodroot, dogtooth violet, marsh marigold, buttercup, tulip 
tree, horse-chestnut, Jeffersonia, May-apple, cherry, apple, crocus, tulip, 
daffodil, primrose, wild ginger, cranesbill, locust, bluebell. 



STRUCTURE OF THE ELOWER AND ITS ORGANS 207 
220. Review Summary of Chapter XV.^ 



Kinds of flowers as regards number of circles or 
sets of organs present 



Kinds as regards numerical plan 



Kinds as regards similarity of parts of the same ( 1. 
circle 12. 

Parts of a stamen 

Parts of a pistil . 



Stamens as regards union with each othei- 

Pistils as regards union with each other . 

Degree of union of separate circles . . 
1 Illustrate by sketches. 



(5; 

3. 

" 1. 
2. 
3. 
4. 

f 1. 

U. 



CHAPTER XVI 



TRUE NATURE OF FLORAL ORGANS; DETAILS OF 
THEIR STRUCTURE; FERTILIZATION 

221. The Flower a Shortened and greatly Modified 
Branch. — In Chapter VIII, the leaf-bud was explained 
as being an undeveloped branch, which in its growth 
would develop into a real branch (or a prolongation of 
the main stem). Now, since flower-buds appear regularly 





Fig. 158. — Transition from Bracts to Sepals in a Cactus Flower. ' 

either in the axils of leaves or as terminal buds, there is 
reason to regard them as of similar nature to leaf-buds. 
This would imply that the receptacle corresponds to the 
axis of the bud shown in Fig. 86, and that the parts of 
the flower correspond to leaves. There is plenty of evi- 
dence that this is really true. Sepals frequently look 
very much like leaves, and in many cacti the bracts 

208 



TRUE NATURE OF FLORAL ORGANS 



209 



about the flower are so sepal-like that it is impossible to 
tell where the bracts end and the sepals begin (Fig. 158). 
The same thing is true of sepals and petals in such flowers 
as the white water-lily. In this flower there is a remark- 
able series of intermediate steps, ranging all the way from 
petals, tipped with a bit of anther, through stamens with 
a broad petal-like filament, to regular stamens, as is shown 
in Fig. 159, E^ F, (^, H. The same thing is shown in 




Fig. 159. — Transitions from Petals to Stamens in White Water-Lily. 
E, F, G, H, various steps between petal and stamen. 



many double roses. In completely double flowers all the 
essential organs are transformed by cultivation into petals. 
In the flowers of the cultivated double cherry the pistils 
occasionally take the form of small leaves, and some roses 
turn wholly into green leaves. 

Summing up, then, we know that flowers are altered 
and shortened branches : (1) because flower-buds have as 
regards position, the same kind of origin as leaf-buds ; 
(2) because all the intermediate steps are found between 
bracts, on the one hand, and stamens, on the other ; (3) 



210 FOUNDATIONS OF BOTANY 

because the essential organs are found to be replaced by 
petals or even by green leaves. 

The fact that leaves should be so greatly modified as 
they are in flowers and given work to do wholly different 
from that of the other kinds of leaves so far studied need 
not strike one as exceptional. In many of the most highly 
developed plants below the seed-plants, organs correspond- 
ing to flowers are found, and these consist of modified 
leaves, set apart for the work of reproducing (Sect. 367). 

222. Mode of Formation of Stamens and Pistils from 
Leaves. — It is hardly possible to state, until after Chap- 
ter XXIII has been studied, how stamens stand related 
to leaves.^ 

The simple pistil or carpel is supposed to be made on 
the plan of a leaf folded along the midrib until its margins 
touch, like the cherry leaf in Fig. 87. But the student 
must not understand by this statement that the little 
pistil leaf grows at first like an ordinary leaf and finally 
becomes folded in. The united leaf-margins near the tip 
would form the stigma, and the placenta would correspond 
to the same margins, rolled slightly inwards, extending 
along the inside of the inflated leaf-pouch. Place several 
such folded leaves upright about a common center, and 
their cross-section would be much like that of B in Fig. 
154. Evidence that carpels are really formed in this way 
may be gained from the study of such fruits as that of 
the monkshood (Fig. 168), in which the ripe carpels may 
be seen to unfold into a shape much more leaf-like than 
that which they had while the pistil was maturing. What 

1 "The anther answers exactly to the spore-cases of the ferns and their 
allies, while the filament is a small specialized leaf to support it." For a 
fuller statement, see Potter and Warming's Systematic Botany, pp. 236, 237. 



TKUE NATUKE OF FLOKAE ORGANS 



211 




really occurs is this: the flower-bud, as soon as it has 
developed far enough to show the first rudiments of the 
essential organs, contains them in the form of minute 
knobs. These are developed from the tissues of the plant 
in the same manner as are the knobs in a leaf-bud, which 
afterwards become leaves (Fig. 87, II) ; but as growth 
and development progress 
in the flower-bud, its con- 
tents soon show themselves 
to be stamens and pistils (if 
the flower is a perfect one). 
223. The Anther and its 
Contents. — Some of the 
shapes of the anthers may 
be learned from Figs. 149 
and 160.1 xhe shape of the ^'^- 1«<^— ^^i^^^s of discharging Poiien. 

anther and the way in which ^'J^-^—^pS^^d^S::^ 
it opens depend largely upon 
the way in which the pollen 
is to be discharged and how it is carried from flower tG 
flower. The commonest method is to have the anther- 
cells split lengthwise, as in Fig. 160, I. A few anthers 
open by trap-doors like valves, as in II, and a larger 
number by little holes at the top, as in III. 

The pollen in many plants with inconspicuous flowers, 
as the evergreen cone-bearing trees, the grasses, rushes, 
and sedges, is a fine, dry powder. In plants with showy 
flowers it is often somewhat sticky or pasty. The forms 
of pollen grains are extremely various. Fig. 161 will 
serve to furnish examples of some of the shapes which 



(amaryllis); II, by uplifted^ 

berry); III, by a pore at tbe top of each 

anther-lobe (nightshade). 



1 See Kerner and Oliver's Natural History of Plants, Vol. II, pp. 86-95. 



212 



FOUNDATIONS OF BOTANY 



the grains assume ; c in the latter figure is perhaps as 
common a form as any. Each pollen grain consists mainly 
of a single cell, and is covered by a moderately thick outer 
wall and a thin inner one. Its contents are thickish 
protoplasm, full of little opaque particles and usually 
containing grains of starch and little drops of oil. The 
knobs on the outer coat, as shown in Fig. 161 J, mark 




a be 

Flu. IGl. — Pollen Grains. (Very greatly magnified.) 
a, pumpkin ; b, enchanter's nightshade ; c, Albuca ; d, pink ; e, hibiscus. 

the spots at which the inner coat of the grain is finally 
to burst through the outer one, pushing its way out in 
the form of a slender, thin-walled tube.^ 

224. The Formation of Pollen Tubes. — This can be 
studied in pollen grains which have lodged on the stigma 
and there been subjected to the action of its moist surface. 
It is, however, easier to cause the artificial production of 
the tubes. 

EXPERIMENT XXXVIII 



Production of Pollen Tubes. — Place a few drops of suitably diluted 
syrup with some fresh pollen in a concave cell ground in a micro- 
scope slide ; cover with thin glass circle ; place under a bell-glass, 
with a wet cloth or sponge, to prevent evaporation of the syrup, and 
set aside in a warm place, or merely put some pollen in syrup in a 

1 See Keruer and Oliver's Natural History of Plants, Vol. II, pp. 95-104. 



FERTILIZATION 



213 



watch crystal under the bell-glass. Examine from time to time to 
note the appearance of the pollen tubes. Try several kinds of 
pollen if possible, using syrups of various strengths. The follow- 
ing kinds of pollen form tubes readily in syrups of the strengths 
indicated. 

Tulip . . . . . . . 1 to 3 per cent. 

Narcissus . . . . . . . 3 to 5 " 

Cytisus canariensis (called Genista by florists) 15. " 

Chinese primrose 10 " 

Sweet pea i 10 to 15 " 

Tropseolumi 15 " 



225. Microscopical Structure of the Stigma and Style. — 

Under a moderate power of the microscope the stigma is 

seen to consist of cells set irregularly over the surface, 

and secreting a moist liquid to 

which the pollen grains adhere (Fig. 

162). Beneath these superficial cells 

and running down through the style 

(if there is one) to the ovary is 

spongy parenchyma. In some pistils 

the pollen tube proceeds through 

the cell walls, which it softens by 

means of a substance which it exudes 

for that purpose. In other cases 

(Fig. 163) there is a canal or passage, 

along which the pollen tube travels 

on its way to the ovule. 




Fig. 162. — Stigma of Thorn- 
Apple {Datura) with Pollen. 
(Magnified.) 



1 The sweet-pea pollen and that of Tropseolum are easier to manage than 
any other kinds of which the author has personal knowledge. If a concaved 
slide is not available, the cover-glass may be propped up on bits of the thin- 
nest broken cover-glasses. From presence of air or some other reason, the 
formation of pollen tubes often proceeds most rapidly just inside the margin 
of the cover-glass. 



214 



FOUNDATIONS OF BOTANY 



226. Fertilization. — By fertilization in seed-plants the 
botanist means the union of a generative cell from a pol- 
p len grain with that of an egg-cell 

at the apex of the embryo sac 
(Fig. 165). This process gives 
rise to a cell which contains 
material derived from the pollen 
and from the egg-cell. In a 
great many plants the pollen, 
in order to accomplish the most 
successful fertilization, must 
come from another plant of the 
same kind, not from the indi- 
vidual which bears the ovules 
that are being fertilized. 

Pollen tubes begin to form 
soon after pollen grains lodge 
on the stigma. The time re- 

FiG. 163. —Pollen Grains producing • i n ,i i i • 

Tubes, on stigma of a Lily. (Much quircd for the proccss to begin 
^^sn^^^^.) varies in different kinds of 

g, pollen grains ; t, pollen tubes ; p, ■, , 

papilla of stigma ;c, canal or pas- plauts, requiring lu many cases 

twenty-four hours or more. The 
length of time needed for the 
pollen tube to make its way 
through the style to the ovary 
depends upon the length of the 
style and other conditions. In 
the crocus, which has a style 
several inches long, the descent 
takes from one to three days. 

Finally the tube penetrates the opening at the apex of 




sage running toward ovary. 




Fig. 1G4. — Pollen Grain of Snow- 
flake (Leucoium) producing a Pol- 
len Tube with Two Naked Genera- 
tive Cells. 



FERTILIZATION 



215 



the ovule m, in Fig. 165, reaches one of the cells shown 
at 6, and transfers a generative cell into this egg-cell. The 
latter is thus enabled to 
divide and grow rapidly 
into an embryo. This 
the cell does by forming 
cell-walls and then in- 
creasing by continued 
subdivision, in much the 
same way in which the 
cells at the growing point 
near the tip of the root, 
or those of the cambium 
layer, subdivide.^ 

227. Nature of the 
Fertilizing Process. — 
The necessary feature of 
the^ process of fertiliza- 
tion is the union of the 
essential contents of two 
cells to form a new one, 
from which the future 
plant is to sprifig. This 
kind of union is found 
to occur in many cryp- 
togams (Chapters 
XX- XXII), resulting 
in the production of 
a spore capable of grow- 
ing into a complete plant like that which produced it. 

1 See Kerner and Oliver's Natural History of Plants^ Vol. II, pp. 401-420. 




Fig. 165. — Diagrammatic Representation of 
Fertilization of an Ovule. 

i, inner coating of ovule ; o, outer coating of 
ovule; 1), pollen tube, proceeding from one 
of the pollen grains on the stigma ; c, the 
place where the two coats of the ovule 
blend. (The kind of ovule here shown is 
inverted, its opening m being, at the bottom, 
and the stalk / adhering along one side of 
the ovule.) a to e, embryo sac, full of pro- 
toplasm ; a, so-called antipodal cells of em- 
bryo sac ; n, central nucleus of the embryo 
sac ; e, nucleated cells, one of which, the 
egg-cell, receives the essential contents of 
the pollen tube ; /, funiculus or stalk of 
ovule ; TO, opening into the ovule. 



216 FOUNDATIONS OF BOTANY 

228. Number of Pollen Grains to Each Ovule. — Only 
one pollen tube is necessary to fertilize each ovule, but 
so many pollen grains are lost that plants produce many 
more of them than of ovules. The ratio, however, varies 
greatly. In the night-blooming cereus there are about 
250,000 pollen grains for 30,000 ovules, or rather more 
than 8 to 1, while in the common garden wistaria there 
are about 7000 pollen grains to every ovule, and in Indian 
corn, the cone-bearing evergreens, and a multitude of other 
plants, many times more than 7000 to 1. These differences 
depend upon the mode in which the pollen is carried from 
the stamens to the pistil. 



CHAPTER XVII 
THE STUDY OF TYPICAL FRUITS 

229. A Berry, the Tomato.^ — Study the external form of the 
tomato, and make a sketch of it showing the persistent calyx and 
peduncle. 

Cut a cross-section at about the middle of the tomato. Note the 
thickness of the epidermis (peel oif a strip) and of the wall of the 
ovary. Note the number, size, form, and contents of the cells of 
the ovary. Observe the thickness and texture of the partitions 
between the cells. Sketch. 

Note the attachments of the seeds to the placentas and the gelati- 
nous, slippery coating of each seed. 

The tomato is a typical berry, but its structure presents fewer 
points of interest than are found in some other fruits of the same 
general character, so the student will do well to spend a little more 
time on the examination of such fruits as the orange or the lemon. 

230. A Hesperidium, the Lemon. — Procure a large lemon which 
is not withered, if possible one which still shows the remains of the 
calyx at the base of the fruit. 

Note the color, general shape, surface, remains of the calyx, 
knob at portion formerly occupied by the stigma. Sketch the fruit 
about natural size. Examine the pitted surface of the rind with 
the magnifying glass and sketch it. Remove the bit of stem and 
dried-up calyx from the base of the fruit; observe, above the calyx, 
the knob or disk on which the pistil stood. Note with the magni- 
fying glass and count the minute whitish raised knobs at the bottom 
of the saucer-shaped depression left by the removal of the disk. 
What are they ? 

1 Fresh tomatoes, not too ripe, are to be used, or those which have been kept 
over from the previous summer in formalin solution. The very smallest 
varieties, such as are often sold for preserving, are as good for study as the 
larger kinds. 

217 



218 FOUNDATIONS OF BOTANY 

Make a transverse section of the lemon, not more than a fifth of 
the way down from the stigma end and note : 

(1) The thick skin, pale yellow near the outside, white within. 

(2) The more or less wedge-shaped divisions containing the juicy 
pulp of the fruit. These are the matured cells of the ovary ; count 
these. 

(3) The thin partition between the cells. 

(4) The central column or axis of white pithy tissue. 

(5) The location and attachment of any seeds that may be 
encountered in the section. 

Make a sketch to illustrate these points, comparing it with 
Fig. 171. 

Study the section with the magnifying glass and note the little 
spherical reservoirs near the outer part of the skin, which contain the 
oil of lemon which gives to lemon peel its characteristic smell and 
taste. Cut with the razor a thin slice from the surface of a lemon 
peel, some distance below the section, and at once examine the 
freshly cut surface with a magnifying glass to see the reservoirs, 
still containing oil, which, however, soon evaporates. On the cut 
surface of the pulp (in the original cross-section) note the tubes in 
which the juice is contained. These tubes are not cells, but their 
walls are built of cells. Cut a fresh section across the lemon, about 
midway of its length and sketch it, bringing out the same points 
which were shown in the previous one. The fact that the number 
of ovary cells in the fruit corresponds with the number of minute 
knobs in the depression at its base is due to the fact that these 
knobs mark the points at which fibro-vascular bundles passed from 
the peduncle into the cells of the fruit, carrying the sap by which 
the growth of the latter was maintained. 

Note the toughness and thickness of the seed-coats. Taste the 
kernel of the seed. 

Cut a very thin slice from the surface of the skin, mount in 
water, and examine with a medium power of the microscope. 
Sketch the cellular structure shown and compare it with the sketch 
of the corky layer of the bark of the potato tuber. 

Of what use to the fruit is a corky layer in the skin ? (See Sect. 
453 for further questions.) 



THE STUDY OF TYPICAL FRUITS 219 

231. A Legume, the Bean-Pod.^ — Lay the pod flat on the table 
and make a sketch of it, about natural size. Label stigma, style, 
ovary, calyx, peduncle. 

Make a longitudinal section of the pod, at right angles to the 
plane in which it lay as first sketched, and make a sketch of the 
section, showing the partially developed seeds, the cavities in which 
they lie, and the solid portion of the pod between each bean and 
the next. 

Split another pod, so as to leave all the beans lying undisturbed 
on one-half of it and sketch that half, showing the beans lying in 
their natural position and the funiculus or stalk by which each is 
attached to the placenta ; compare Fig. 271. 

Make a cross-section of another pod, through one of the beans, 
sketch the section, and label the placenta (formed by the united 
edges of the pistil leaf) and the midrib of the pistil leaf. 

Break off sections of the pod and determine, by observing where 
the most stringy portions are found, where the fibro-vascular bundles 
are most numerous. 

Examine some ripe pods of the preceding year,^ and notice where 
the dehiscence, or splitting open of the pods, occurs, whether down 
the placental edge, ventral suture, the other edge, dorsal suture, or 
both. 

232. An Akene, the Fruit of Dock. — Hold in the forceps a ripe 
fruit of any of the common kinds of dock," and examine with the 
magnifying glass. Note the three dry, veiny, membranaceous sepals 
by which the fruit is enclosed. On the outside of one or more of 
the sepals is found a tubercle or thickened appendage which looks 
like a little seed or grain. Cut off the tubercles from several of the 
fruits, put these, with some uninjured ones, to float in a pan of 
water, and watch their behavior for several hours. What is appar- 
ently the use of the tubercle ? 

1 Any species of bean (Phaseolus) will answer for this study. Specimens 
in the condition known at the markets as " shell-beans " would be best, but 
these are not obtainable in spring. Ordinary *' string-beans " will do. 

2 Which may be passed round for that purpose. They should have been 
saved and dried the preceding autumn. 

3 Runiex crispus, R. obtusifoUus, or R. verticillatus. This should have 
been gathered and dried the preceding summer. 



220 FOUNDATIONS OF BOTANY 

Of what use are the sepals, after drying up ? Why do the fruits 
cling to the plant long after ripening? 

Carefully remove the sepals and examine the fruit within them. 
What is its color, size, and shape? Make a sketch of it as seen with 
the magnifying glass. N'ote the three tufted stigmas, attached by 
slender threads to the apex of the fruit. What does their tufted 
shape indicate ? 

What evidence is there that this seed-like fruit is not really a 
seed? 

Make a cross-section of a fruit and notice whether the wall of 
the ovary can be seen, distinct from the seed-coats. Compare the 
dock fruit in this respect with the fruit of the buttercup, shown in 
Fig. 166. Such a fruit as either of these is called an akene. 



CHAPTER XVIII 
THE FRUIT 1 

233. What constitutes a Fruit. — It is not easy to make 
a short and simple definition of what botanists mean by 
the tevm fruit. It has very little to do with the popular 
use of the word. Briefly stated, the definition may be 
given as follows : The fruit consists of the matured ovary 
and contents^ together with any intimately connected parts. 
Botanically speaking, the bur of beggar's ticks (Fig. 273), 
the three-cornered grain of buckwheat, or such true grains 
as wheat and oats, are as much fruits as is an apple or a 
peach. 

The style or stigma sometimes remains as an important 
part of the fruit in the shape of a hook, as in the common 
hooked crowfoot ; or in the shape of a plumed appendage, 
as in the virgin's bower, often called wild hops. The 
calyx may develop hooks, as in the agrimony, or plumes, 
as in the thistle, the dandelion, lettuce, and man}^ other 
familiar plants. In the apple, pear, and very many ber- 
ries, the calyx becomes enlarged and pulpy, often consti- 
tuting the main bulk of the mature fruit. The receptacle 
not infrequently, as in the apple, forms a more or less 
important part of the fruit. 

234. Indehiscent and Dehiscent Fruits. — All of the 
fruits considered in the next three sections are i7idehiscent, 

1 See Gray's Structural Botany, Chapter VII, also Kerner and Oliver's 
Natural History of Plants, Vol. II, pp. 427-438. 

221 



222 



FOUNDATIONS OF BOTANY 




Fig. 166. — Akenes of a Buttercup. 

A, head of akenes ; B, section of a single 

akene (magnified) ; a, seed. 



that is, they remain closed after ripening. Dehiscent 
fruits when ripe open in order to discharge their seeds. 

The three classes which im- 
mediately follow Sect. 237 
belong to this division. 

235. The Akene. — The 
one-celled and one-seeded 
pistils of the buttercup, 
strawberry, and many other 
flowers, ripen -into a little 
fruit called an akene (Fig. 
166). Such fruits, from 
their small size, their dry 
consistency, and the fact that they never open, are usually 
taken for seeds by those who are not botanists. 

In the group of plants to which the daisy, the sunflower, 
and the dandelion belong, the akenes consist of the ovary 
and the adherent calyx tube. The limb of the calyx is 
borne on the summit of many akenes, sometimes in the form 
of teeth, sometimes as a tuft 
of hairs or bristles (Fig. 267). 

236. The Grain. — Grains, 
such as corn, wheat, oats, bar- 
ley, rice, and so on, iiave the 
interior of the ovary com- 
pletely filled by the seed, and 
the seed-coats and the wall of 
the ovary are firmly united, as 
shown in Fig. 6. 

237. The Nut. — A nut (Fig. 167) is larger than an 
akene, usually has a harder shell, and commonly contains 




Fig. si 67. — Chestnuts. 



THE FEUIT 



223 




a seed which springs from a single ovule of one cell of a 
compound ovary, which develops at the expense of all the 
other ovules. The chestnut-bur is a kind of involucre, 
and so is the acorn-cup. The name 
nut is often incorrectly applied in 
popular language; for example, the 
so-called Brazil-nut is really a large 
seed with a very hard testa. 

238. The Follicle. — One-celled, 
simple pistils, like those of the marsh 
marigold, the columbine, and a good 
many other plants, often produce a 
FiG.168.— Group of Foiii- fruit which deliisccs along a single 
cies and a Single Follicle guturc, usually the vcutral one. Such 

of the Monkshood. -^ 

a fruit is called 2i follicle (Fig. 168). 

239. The Legume. — A legume is a one-celled pod, 
formed by the maturing of a simple pistil, which dehisces 
along both of its sutures, as already seen in the case of 
the bean pod, and illus- 
trated in Fig. 271. 

240. The Capsule.— 
The dehiscent fruit 
formed by the ripening 
of a compound pistil is 
called a capsule. Such 
a fruit may be one- 
celled, as in the linear 
pod of the celandine 
(Fig. 271), or several- 
celled, as in the fruit of the poppy, the morning-glory, 
and the jimson weed (Fig. 271). 




II 

Fig. 169. — Winged Fruits, 
I, elm ; II, maple. 



224 



FOUNDATIONS OF BOTANY 



241. Dry Fruits and Fleshy Fruits. — In all the cases 
discussed or described in Stects. 238-240, the wall of the 
ovary (and the adherent calyx when present) ripen into 
tissues which are somewhat hard and dry. Often, how- 
ever, these parts become developed into a juicy or fleshy 
mass by which the seed is surrounded ; hence a general 
division of fruits into dry fruits and fleshy fruits. 

242. The Stone-Fruit. — In the peach, apricot, plum, and 
cherry, the pericarp or wall of the ovary, during the proc- 
ess of ripening, becomes con- 
verted into two kinds of tissue, 
the outer portion pulpy and 
edible, the inner portion of 
almost stony hardness. In 
common language the hard- 
ened inner layer of the peri- 
carp, enclosing the seed, is 
called the stone (Fig. 170), 
hence the name stone-fruits. 

243. The Pome. —The fruit 
of the apple, pear, and quince is called a pome. It con- 
sists of a several-celled ovary, — the seeds and the tough 
membrane surrounding them in the core^ — enclosed by a 
fleshy, edible portion which makes up the main bulk of 
the fruit and is formed from the much-thickened calyx, 
with sometimes an enlarged receptacle. In the apple and 
the pear much of the fruit is receptacle. 

244. The Pepo or Gourd-Fruit. — In the squash, pump- 
kin, and cucumber, the ripened ovary, together with the 
thickened adherent calyx, makes up a peculiar fruit (with 
a Arm outer rind) known as the pepo. The relative bulk 




Fig. 170. — Peach. Longitudinal 
Section of Fruit. 



THE FRUIT 



225 



of enlarged calyx and of ovary in such fruits is not always 
the same. 

How does the amount of material derived from fleshy 
and thickened placentae in the squash compare with that 
in the watermelon ? 

245. The Berry. — The berry proper, such as the 
tomato, grape, persimmon, gooseberry, currant, and so on, 
consists of a rather thin- o 

skinned, one- to several- 
celled, fleshy ovary and its 
contents. In the first three 
cases above mentioned the 
calyx forms no part of the 
fruit, but it does in the last 
two, and in a great number 
of berries. 

The gourd-fruit and the 
hesperidium, such as the 
orange (Fig. 171), lemon, 
and lime, are merely de- 
cided modifications of the 
berry proper. 

246. Aggregate Fruits. 




Fig. 171. — Cross-Section of auOrauge. 
;, axis of fruit with dots showing cut-off 
ends of flbro-vascular bundles ; p, parti- 
tion between cells of ovary ; S, seed ; 
c, cell of ovary, filled with a pulp com- 
posed of irregular tubes, full of juice ; 
o, oil reservoirs near outer surface of 
rind ; e, corky layer of epidermis. 



The 



raspberry, blackberry 
(Fig. 172), and similar fruits consist of many carpels, each 
of which ripens into a part of a compound mass, which, 
for a time at least, clings to the receptacle. The whole is 
called an aggregate fruit. 

To which one of the preceding classes does each unit of 
a blackberry or of a raspberry belong ? 

What is the most important difference in structure 
between a fully ripened raspberry and a blackberry ? 



226 



FOUNDATIONS OF BOTANY 



247. Accessory Fruits and Multiple Fruits. — Not infre- 
quently, as in the strawberry (Fig. 172), the main bulk of 
the so-called fruit consists neither of the ripened ovary 
nor its appendages. Such a combination is called an 
accessory fruit. 

Examine with a magnifying glass the surface of a small, unripe 
strawberry, then that of a ripe one, and finally a section of a ripe 
one, and decide where the separate fruits of the strawberry are found, 
what kind of fruits they are, and of what the main bulk of the straw- 
berry consists. 

The fruits of two or more separate flowers may blend 
into a single mass, which is known as a multiple fruit. 
Perhaps the best-known edible examples of this are the 





I II III 

Fig. 172.— I, Strawberry ; II, Raspberry ; III, Mulberry. 

mulberry (Fig. 172) and the pineapple. The last-named 
fruit is an excellent instance of the seedless condition 
which not infrequently results from long-continued culti- 
vation. 

248. Summary. — The student may find it easier to 
retain what knowledge he has gained in regard to fruits if 
he copies the following synopsis of the classification of 
fruits, and gives an example of each kind. 



THE FKUIT 



227 



Fruits 



Composition 



Texture 



Mode of 
disseminating seed 



r Simple 
I Asfyrr 



Aggregate. 
Accessory. 
Multiple. 



Fleshy 



Stone 



Dry 



Indehiscent 



Dehiscent 



fi. 

is. 



CHAPTER XIX 
THE CLASSIFICATION OF PLANTS ^ 

249. Natural Groups of Plants. — One does not need to 
be a botanist in order to recognize the fact that plants 
naturally fall into groups which resemble each other pretty 
closely, that these groups may be combined into larger 
ones the members of which are somewhat alike, and so on. 
For example, all the bulb-forming spring buttercups ^ which 
grow in a particular field may be so much alike in leaf, 
flower, and fruit that the differences are hardly worth 
mentioning. The tall summer buttercups ^ resemble each 
other closely, but are decidedly different from the bulbous 
spring-flowering kind, and yet are enough like the latter 
to be ranked with them as buttercups. The yellow 
water-buttercups^ resemble in their flowers the two 
kinds above mentioned, but differ from them greatly in 
habit of growth and in foliage, while still another, a 
very small-flowered kind,^ might fail to be recognized 
as a buttercup at all. 

The marsh marigold, the hepatica, the rue anemone, 
and the anemone all have a family resemblance to butter- 
cups,^ and the various anemones by themselves form 
another group like that of the buttercups. 

1 See Warming and Potter's Systematic Botany, Strasburger, Noll, Schenk, 
and Schiraper's Text-Book of Botany, Part II, or Kerner and Oliver, Vol. II, 
pp. 616-790. 2 jR. hulhosus. 3 ji^ acris. * E. multifidus. 5 n, dbortivus. 

6 Fresh specimens or herbarium specimens will show this. 

228 



THE CLASSIFICATION OF PLANTS 229 

250. Genus and Species. — Such a group as that of the 
buttercups is called a genus (plural genera)^ while the 
various kinds of buttercups of which it is composed are 
called species. The scientific name of a plant is that of the 
genus followed by that of the species. The generic name 
begins with a capital, the specific does not, unless it is a 
substantive. After the name comes the abbreviation for 
the name of the botanist who is authority for it; thus the 
common elder is Samhucus canadensis^ L., L. standing for 
Linnseus. Familiar examples of genera are the Violet 
genus, the Rose genus, the Clover genus, the Golden-rod 
genus, the Oak genus. The number of species in a genus 
is very various, — the Kentucky Coffee-tree genus con- 
tains only one species, while the Golden-rod genus com- 
prises more than forty species in the northeastern United 
States alone. 

251. Hybrids. — If the pollen of a plant of one species 
is placed on the stigma of a plant of the same genus but a 
different species, no fertilization will usually occur. In a 
large number of cases, however, the pistil will be ferti- 
lized, and the resulting seed will often produce a plant 
intermediate between the two parent forms. This proc- 
ess is called hybridization^ and the resulting plant a 
hybrid. Many hybrid oaks have been found to occur 
in a state of nature, and hybrid forms of grapes, orchids, 
and other cultivated plants, are produced by horticul- 
turists at will. 

252. Varieties. — Oftentimes it is desirable to describe 
and give names to subdivisions of species. All the culti- 
vated kinds of apple are reckoned as belonging to one spe- 
cies, but it is convenient to designate such varieties as the 



230 FOUNDATIONS OF BOTANY 

Baldwin, the Bellflower, the Rambo, the Gravenstein, the 
Northern Spy, and so on. Very commonly varieties do 
not, as horticulturists say, " come true," that is to say, the 
seeds of any particular variety of apple not only are not 
sure to produce that variety, but they are nearly sure to 
produce a great number of widely different sorts. Varie- 
ties which will reproduce themselves from the seed, such 
as pop-corn, sweet corn, flint-corn, and so on, are called 
races. 

Only long and careful study of plants themselves and 
of the principles of classification will enable any one to 
decide on the limits of the variety, species, or genus, that 
is, to determine what plants shall be included in a given 
group and what ones shall be classed elsewhere. 

253. Order or Family. — Genera which resemble each 
other somewhat closely, like those discussed in Sect. 249, 
are classed together in one order or family. The particu- 
lar genera above mentioned, together with a large number 
of others, combine to make up the Crowfoot family. In 
determining the classification of plants most points of 
structure are important, but the characteristics of the 
flower and fruit outrank others because they are more 
constant, since they vary less rapidly than the characteris- 
tics of roots, stems, and leaves do under changed condi- 
tions of soil, climate, or other surrounding circumstances. 
Mere size or habit of growth has nothing to do with the 
matter, so the botanist finds no difficulty in recognizing 
the strawberry plant and the apple tree as members of 
the same family. 

This family affords excellent illustrations of the mean- 
ing of the terms genus., species, and so on. Put in a 



THE CLASSIFICATION OF PLANTS 



231 



tabular form, some of the subdivisions of the Rose family 
are as follows : 



Plum genus 



Rose genus 



Pear genus 



r Peach species (many varieties). 

j Garden plum species (many varieties). 

Wild black cherry species. 

Garden red cherry species (many varieties) 

Dwarf wild rose 

species. 

Sweet-brier species. 

-r T . r Tea variety, 

India rose species -i ^ 

I Pompon variety, etc 

Damask rose species. 

r r Seckel variety. 

Pear species ■< Bartlett variety 



Apple species 



l^ Sheldon variety, etc. 

Baldwin variety. 
Greening variety, 
Bellflower variety. 
Northern Spy variety, 
etc. 



254. Grouping of Families. — Families are assembled 
into classes^ and these again into larger groups. The 
details of the entire plan of classification are too compli- 
cated for any but professional botanists to master, but an 
outline of the scheme may be given in small space. 

The entire vegetable kingdom is divided into two great 
divisions, the first consisting of cri/ptogams or sipoxe-plsLuts, 
the second of phanerogams or seed-plants. Here the rela- 
tions of the various subdivisions may best be shown by a 
table.i 



1 This is, of course, only for consultation, not to be committed to memory. 



232 



FOUNDATIONS OF BOTANY 



>^ S 1 

o < ^ 

M O P-i 

g g « 

- ^ s 



THE CLASSIFICATION OF PLANTS 



233 



Division II 
Phanerogams or \ 
Seed-Plants 



Class I 
Gymnosperms or seed-plants with naked ova- 
ries, such as pines, spruces, cedars, and many 
other evergreen trees. 

Subclass I 
Class II Monocotyledonous 

Angiosperms or Plants 

seed-plants with i Subclass II 

closed ovaries i Dicotyledonous 
Plants 



256. The Groups of Cryptogams. — The student is not 
to suppose that the arrangement of cryptogams into the 
four great groups given in the preceding table is the only 
way in which they could be classed. It is simply one 
way of dividing up the enormous number of spore-bearing 
plants into sections, each designated by marked character- 
istics of its own. But the amount of difference between 
one group and another is not always necessarily the same. 
The pteridophytes and the bryophytes resemble each 
other much more closely than the latter do the thallo- 
phytes, while the myxothallophytes are but little like other 
plants and it is extremely probable that they are really 
animals. 

The classes given in the table do not embrace all known 
cryptogams, but only those of which one or more repre- 
sentatives are described or designated for study in this 
book. Lichens in one sense hardly form a class, but it is 
most convenient to assemble them under a head by them- 
selves, on account of their extraordinary mode of life, a 
partnership between algse and fungi. 

257. The Classes of Seed-Plants. — The gymnosperms 
are much less highly developed than other seed-plants. 



234 FOUNDATIONS OF BOTANY 

The angiosperms constitute the great majority of seed- 
plants (or, as they have been more commonly called, 
flowering plants). Only one family of gymnosperms (the 
Conifer ce) is described in Part III of this book, though 
there are other families of great interest to the botanist, 
but with no representatives growing wild in the Northern 
United States. 

When people who are not botanists speak of plants 
they nearly always mean angiosperms. This class is more 
interesting to people at large than any other, not only on 
account of the comparatively large size and the con- 
spicuousness of the members of many families, but also 
on account of the attractiveness of the flowers and fruit 
of many. Almost all of the book which precedes the 
present chapter (except Chapter XII) has been occupied 
with seed-plants. 

Seed-plants of both classes frequently offer striking 
examples of adaptation to the conditions under which 
they live, and these adaptations have lately received much 
study, and are now treated as a separate department of 
botany (see Part II). 



CHAPTER XX 
TYPES OF CRYPTOGAMS; THALLOPHYTES 

258. The Group Thallophytes. — Under this head are 
classed all the multitude of cryptogams which have a 
plant-body without true roots, stems, or leaves. Such a 
plant-body is called a thallus. In its simplest form it con- 
sists of a portion of protoplasm not enclosed in a cell-wall 
and without much of any physiological division of labor 
among its parts (Fig. 125). Only a little less simple are 
such enclosed cells as that of Pleiirococcus (Sect. 278) or 
one of the segments of Oseillatoria (Sect. 268). The most 
com.plex thallophytes, such as the higher algse and fungi, 
have parts definitely set aside for absorption of food and 
for reproduction. The latter is sometimes accomplished 
by more than one process and is occasionally aided by 
some provision for scattering the reproductive bodies or 
spores about when they are mature. 

259. Spores. — Before beginning the study of spore- 
plants it is well for the student to know what a spore is. 
A spore is a cell which becomes free and capable of develop- 
ing into a new plant. Spores are produced in one of two 
ways : either asexually^ from the protoplasm of some part 
of the plant (often a specialized spore-producing portion), 
or sexually^ by the combination of two masses of proto- 
plasm, from two separate plants, or from different parts of 
the same plant. 

235 



236 FOUNDATIONS OF BOTANY 

Asexually produced spores are sometimes formed, each 
by the condensation of the protoplasm of a single cell, as 
shown in Fig. 174, E. They are also formed by the con- 
tents of spore-cases breaking up into many spores (Fig. 
173, B', Fig. 210, B). Spores are sometimes produced by 
the spontaneous division of a mass of protoplasm into a 
small definite number of segments (Fig. 188, t). Spores 
which have the power of moving (swimming) freely are 
known as zoospores (Fig. 179, ^). 

Sexually produced spores are formed in many ways. 
One of the simplest modes is that shown in Fig. 178, 
resulting in zygospores. Other methods are illustrated in 
Figs. 185 and 187.i 

THE STUDY OF SLIME MOULDS 2 

260. Occurrence. — Slime moulds occur in greenhouses, in tan- 
yards, or on old logs and decaying leaves in woods. They may be 
cultivated in the laboratory. 

They have been described in their vegetative condition on page 179. 

261. Examination with the Magnifying Glass. — Stemonitis is one 
of the most available genera to illustrate the fruiting of slime moulds. 
At maturity the motile protoplasm of the vegetative stage quickly 
transforms itself into numerous sporangia or spore-cases with dust- 
like spores. With the naked eye and with a magnifying glass note 
the color, form, and feathery appearance of the spore-case of Stemo- 
nitis. The outer wall disappears at an early stage, leaving only an 
inner structure and spores. Sketch the general outline under a 
magnifying glass. 

262. Examination with the Microscope. — With a low power of 
the microscope sketch the network of branching hairs which com- 
pose the structure of the sporangium. Note the presence or absence 

i See Vine's Student's Text-Book of Botany, pp. 68-71. 
2 This should logically precede Sect. 258. 



TYPES OF CRYPTOGAMS: THALLOPHYTES 



237 



of a central column. Have any of the branches free tips ? With a 
power of 250 or more examine the spores. A much higher power 
may be used to advantage. Describe the surface of the spore. 



THE STUDY OF BACTERIA 

263. Occurrence. — " Bacteria may occur anywhere but not every- 
where." Tn water, air, soil, and almost any organic substance, living 





Fig. 173. — Spore-Cases of Slime Moulds. 

A, a group of spore-cases of Arcyria; B, a spore-case of Trichia, bursting open 
and exposing its spores to tlie wind, x 20 ;" C, threads of the same, with spores 
between them > x 250. 



or dead, some species of plant belonging to the group Bacteria may 
occur. A small banch of hay placed in a tumbler of water will, at a 
suitable temperature, yield an abundant crop in a few days or hours. 
Raw peas or beans soaked for a week or two in water in a warm 
place will afford a plentiful supply. 

264. Cultures. — Pure cultures of bacteria are commonly made in 
some preparation of gelatine in sterilized test-tubes. Boiled potatoes 
serv^ a good purpose for simple (but usually not pure) cultures. 

Select a few small roundish potatoes with skins entire and boil 
in water for a sufficient time to cook them through. Cut them in 
halves with a knife well scalded or sterilized, i.e., freed from all living 



238 FOUNDATIONS OF BOTANY 

organisms in a flame, and lay each on a saucer, with cut surface up, 
covering each with a glass tumbler. The tumblers and saucers 
should be well scalded or kept in boiling water for half an hour and 
used without wiping. Sterilization may be improved by baking 
them in an oven for an hour. 

265. Inoculation. — The cultm^e media prepared as above may 
now be inoculated. Uncover them only when necessary and quickly 
replace the cover. Scrape a little material from the teeth, tongue, 
kitchen sink, floor of house or schoolroom, or any other place you 
may desire to investigate. With the point of a knife blade or a 
needle sterilized in a flame, inoculate a particle of the material to be 
cultivated into tlie surface of one of the potatoes. Several cultures 




%>■* 



\ 



^ 



BCD -E . 

Fig. 174. — Bacteria stained to sliow Cilia. 

A, Bacillus subtilis ; B, Bacillus typhi (the bacillus of typhoid fever) ; C, Bacillus 
tetani (the bacillus which causes lockjaw) ; D, Spirillum undula; E, Bacillus 
tetani forming spores. (All five are magnified 1000 diameters.) 

may be made in this way and one or more left uninoculated as 
checks. Another may be left uncovered in the air for half an hour. 
Others may be made with uncovered potatoes. Kumber each culture 
and keep a numbered record. 

Keep watch of the cultures, looking at them daily or oftener. As 
soon as any change is noticed on the surface of a culture, make a 
descriptive note of it and continue to record the changes which are 
seen. Note the color of the areas of growth, their size, outline, ele- 
vation above the surface, and any indications of wateriness. Any 
growth showing peculiar colors or other characters of special inter- 
est may be inoculated into freshly prepared culture media, using 
any additional precautions that are practicable to guard against 
contamination. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 239 

266. Microscopic Examination. — Examine some of the cultui-es. 
Place a particle of the growth on a slide, dilute it with a drop of 
clear water, and place a cover-glass over it. Examine with the 
highest obtainable power of the microscope, at least ^ in. objective. 
Note the forms and movements, also the sizes if practicable, of any 
bacteria that are found. 



THE STUDY OF OSCILLATORIA i 

267. Occurrence. — Oscillatoria may occur floating in stagnant 
water or on damp soil in ditches, roadsides, dooryards, paths, or 
pots in greenhouses. Other nearly related plants occur on surfaces 
of ponds sometimes covering considerable areas or adhering in small 
spheres to submerged vegetation. Algag of this class are particu- 
larly noxious in water supplies, as they partake of the nature of 
bacteria, to which they are related. 

268. Examination with the Microscope. — After washing a particle 
of Oscillatoria material in a drop of water to remove as much of the 
earth as possible, place it in a clean drop of water, pull to shreds 
with needles, cover, and examine under a power of 200 or more 
diameters. 

Note the color and compare it with chlorophyll green. 

The filament is not one plant, but each of the cells which com- 
pose it is one plant. They are packed together in the filament like 
coins and sometimes may be found separating singly. The usual 
mode of reproduction is by the separation of a number of adhering 
cells as a short filament from one end of a longer one, and this 
increases in length by the dividing of its individual cells. 

269. Movement. — At ordinary temperatures, favorable to growth, 
movement may be observed in the filaments. Describe the move- 
ment. What has it to do with the name of the plant ? 

1 A genus of the class Schizophycex. 



240 



FOUNDATIONS OF BOTANY 



THE STUDY OF DIATOMS 

270. Occurrence. — Diatoms of different species may be found in 
sediment in water in various kinds of places or mixed with or 

adhering to fresh-water or ma- 
rine algse, in ponds and ditches 
or on sand or earth at the 
bottom of clear brooks. In the 
last place they may be detected 
with the eye, forming a yellow- 
ish coloring. They may often 
be obtained by straining hy- 
drant water. Where diatoms 
have been very abundant their 
remains sometimes form beds 
of rock, and fossil diatoms 
compose some of the polishing 
powders of commerce. 

271. Microscopical Exainina- 
tion of Diatoms. — Place a drop 
of water containing diatoms on 
a slide and put a cover-glass 
over it. Examine with a power 
of 200 or more diameters. Dia- 
toms occur singly, resembling- 
triangles, wheels, boats, rods, 
and a great variety of other 
forms (Fig. 176), or adhering 
in long bands, as spokes of a 
wheel, etc. The boat-shaped 
kinds are among the common- 
est. The color of the contents 
is yellowish. The cell-wall is 
encrusted with a shell of silica 
whose surface is covered with beautiful markings, dots or lines, 
which are conspicuous in some species, in others so minute that the 
most powerful microscopes are required to detect them. By boiling 




Fig. 175. — Schizophyceae. 
A, a filament of Calothrix, reproducing by 
hormogonia, h, segmented portions which 
escape from the sheath of the filament ; 
B, Rivularia. (Both A and B greatly 
magnified.) 



TYPES 0^ CRYPTOGAMS; THALLOPHYTES 



241 



in nitric acid, the cellulose wall and its contents may be destroyed 
and the markings of the siliceous shell more easily observed. Each 
diatom consists of a single cell. 

272. Movements of Diatoms. — Living diatoms exhibit a peculiar 
power of movement. In the boat-shaped species the movement is 
much like that of a row-boat, forward or backward. 



THE STUDY OF SPIROGYRA 

273. Occurrence. — Spirogyra, one of the plants commonly known 
as pond-scum, or " frog-spit," occurs widely distributed throughout 
the country in ponds, springs, 
and clear streams. It is of a 
green or yellowish-green color, 
and in sunny weather usually 
floats on or near the surface of 
the water, buoyed up by the 
numerous oxygen bubbles which 
it sets free. It may be found 
flourishing in unfrozen springs, 
even in midwinter. 

274. Examination with the 
Magnifying Glass. ^ — Float a 
little of the material in a white 
plate, using just water enough 
to cover the bottom of the latter. 
Study with the magnifying glass 
and note the green color of the 
threads and their great length 
as compared with their thick- 
ness. Are all the filaments about 
equal to each other in diameter ? 

Handle a mass of the material and describe how it feels between 
the fingers. 

275. Examination with the Microscope. — Mount in water under 
a large cover-glass and examine first with a power of about 100 

1 Consult Huxley's Biology and Spalding's Introduction to Botany. 




Fig. 176. —A Group of Diatoms. 

A, Achnanthes; B , Cocconema ; 
C, Meridion; D, 



242 



FOUNDATIONS OF BOTANY 



diameters, then with a power of 200 diameters or more. Note the 
structure of the filaments. Of what is each made up? Compare 
with the structure of Oscillatoria. 

Move the slide so as to trace the whole length of several filaments, 
and, if the unbroken end of one can be found, study and sketch it. 

Study with the higher power a single 
cell of one of the larger filaments and 
ascertain the details of structure. Try 
to discover, by focusing, the exact shape 
of the cell. How do you know that 
the cells are not flat? Count the bands 
of chlorophyll. The number of bands 
is an important characteristic in dis- 
tinguishing one species from another. 
Run in five-per-cent salt solution at 
one edge of the cover-glass (withdraw- 
ing water from the other edge with a 
bit of blotting paper). If any change 
in the appearance of the cell becomes 
evident, make a sketch to show it. 
What has happened to the cell-con- 
tents? Explain the cause of the 
change by reference to what you know 
of osmose. 

On a freshly mounted slide run 
under the cover-glass iodine solution, 
a little at a time, and note its action 
on the nucleus. Is any starch shown 
to be present? If so, just how is it 
distributed through the cell? 

276. Reproduction of Spirogyra. — 
The reproductive process in Spirogyra 
is of two kinds, the simplest being a process of Jission, or cell- 
division. The nucleus undergoes a very complicated series of 
transformations, which result in the division of the protoplasmic 
contents of a cell into two independent portions, each of which is 
at length surrounded by a complete cell-wall of its own. In Fig. 176 




Fig. 177. — Process of Cell-Multi- 
plication in a Species of Pond- 
Scum. (Considerably magnified.) 

A, portion of a filament partly 
separated at a and completely 
so at 6 ; B, separation nearly 
completed, a new partition of 
cellulose formed at a; C, 
another portion more magni- 
fied, showing mucous covering 
d, general cell-wall c, and a 
delicate membrane a, which 
covers the cell-contents b. 



TYPES OF CilYPTOGAMS; THALLOPHYTES 



243 



the division of the protoplasm and formation of a partition of 
cellulose in a kind of pond-scum are shown, but the nucleus and its 
changes are not represented. 

Another kind of reproduction, namely by conjugation, is found in 
Spirogyra. This process in its simplest form is found in such 
unicellular plants as the desmids 
(Fig. 178). Two cells (apparently 
precisely alike) come in contact, 
undergo a thinning-down or absorp- 
tive process in the cell-walls at the 
point of contact, and finally blend 
their protoplasmic cell-contents, as 
shown in the figure, to form a mass 
known as a spore, or more accu- 
rately a zygospore, from which, after 

A 





Fig. 178. — Conjugation of (Jells of Green Alga;. (Much, maguilied.) 

I. Conjugation of Desmids. A, a single plant in its ordinary condition ; B, empty 
cell-wall of another individual ; C, conjugation of two individuals to form a 
spore by union of their cell-contents. 

II. Conjugation of Spirogyra. A, two filaments of Spirogyra side by side, with 
the contents of adjacent cells uniting to form spores, z. At the bottom of the 
figure the process is shown as beginning at the top as completed, and the cells 
of one filament emptied ; B, a single filament of another kind of Spirogyra, 
containing two spores, one lettered z. {A magnified 240 diameters, B 150 
diameters.) 

a period of rest, a new individual develops. In Spirogyra each 
cell of the filament appears to be an individual and can conjugate 
like the one-celled desmids. It is not easy to watch the process, 
since the spore-formation takes place at night. It is possible, 



244 



FOUNDATIONS OF BOTANY 



however, to retard the occurrence of conjugation by leaving the 
Spirogyra filaments in very cold water over night, and in this way 
the successive steps of the conjugating process may be studied by 
daylight. In such ways the series of phenomena shown in Fig. 
178, II, has been accurately followed. If the student cannot follow 
these operations under the microscope, he may, at least, by looking 
over the yellower portions of a mass of Spirogyra find threads con- 
taining fully formed zygospores, like those shown in B, Fig. 178. 



THE STUDY OF PLEUROCOCCUS 

277. Occurrence. — Pleurococcus may be found on old fences, 
roofs, and many similar places, particularly on the bark of the north 
side of trees. The individual plants cannot be detected by the naked 
eye, but when grouped in masses they form a pow^dery green covering 
over indefinite areas of bark. Plenty are seen where it is moist. 

278. Microscopical Examination of Pleurococcus. — Scrape a minute 
quantity of Pleurococcus from a specimen on bark, place it in a drop 
of water on a slide, distributing it slightly in the water, lay on it 

a cover-glass and ex- 
amine with a power of 
200 or more diameters. 
Sketch with the cam- 
era lucida one of the 
largest cells, some of 
intermediate size, and 
one of the smallest, 
beside several divisions 
of the stage microm- 
eter. 

ISTote the clearly de- 
fined cell-wall of cel- 
lulose, enclosing the 
protoplasmic contents, 
usually green through- 
Do any cells show a nucleus like that in Fig. 179, A ? 





Fig. 179. — Two Cells of Frotococcus. 
(Greatly magnified.) 

A, a spherical cell of the still form ; 5, a motile cell 
with its protoplasm enclosed in a loose cell-wall and 
provided with two cilia. 



out. 



Test the cells with iodine solution for starch. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 245 

INote that in reproduction the cell-contents in many individuals 
has divided into two parts which become separated from each other 
by a cellulose partition. Each of these again divides, and the proc- 
ess continues until thirty-two or more cells may be found in one 
mass or they may fall apart at an earlier stage. 

279. Nutrition of Pleurococcus. — Pleurococcus can flourish only 
with an abundance of light and moisture. In daylight it can absorb 
carbon dioxide and fix carbon (giving of£ the oxygen at the same 
time as bubbles of oxygen) and can assimilate mineral substances. 
It is a capital example of an individual cell capable of independent 
existence. 

280. Motile Forms. — No motile form is known in Pleurococcus. 
Hcematoccus, often known as Protococcus (Fig. 179), is a better object 
for study than Pleurococcus. It may sometimes be found in water 
of stagnant pools, particularly those which contain the drainage of 
barnyards or manure-heaps, in mud at the bottom of eaves-troughs, 
in barrels containing rain-water, or in water standing in cavities in 
logs or stumps. Its presence is indicated by a greenish or some- 
times by a reddish color. It is sometimes found in an actively 
swimming condition, in which case each cell is called a zoospore. 

THE STUDY OF YAUCHERIA 

281. Occurrence. — Species of Vaucheria are found in ponds, 
streams, and pools, immersed or floating like Spirogyra and at all 
seasons may be sought in greenhouses, where they grow on the moist 
earth of beds and pots, forming a green felt. 

282. Examination with the Magnifying Glass. — The magnifying 
glass will show the growth of Vaucheria to consist of numerous 
green filaments similar to those of Spirogyra. Select a small portion 
and spread out the filaments carefully in a drop of water on a slide. 
Does the glass reveal any indications of cross-partitions, of branch- 
ing, or of fruiting organs as short lateral branches ? Does it show 
the form or arrangement of the green coloring matter? 

283. Examination with the Microscope. — Prepare as directed 
for the magnifying glass and place a cover-glass over the prepara- 
tion, with sufficient water. With the lowest power observe the 



246 



FOUNDATIONS OF BOTANY 



continuity of the cell-cavity and (in young plants growing on soil) 
search for root-like portions, in those growing in water for branch- 
ing portions, and fruiting organs in the form of swellings or short 
lateral branches. 

With a power of about thirty to sixty diameters sketch a selected 
plant of moderate extent as nearly complete as possible or else 




Fig. 180. — Vaucheria synandra. 

A, a filament with archegonia and antheridia (considerably magnified) ; B, part 
of same much more highly magnified ; o, oogonium ; a, antheridium ; C, a 
later stage of jB ; D, end of a filament with a zoospore, z, escaping (highly 
magnified). 



sketch a portion showing the branching and a root-like portion. 
Note and indicate the absence or presence and arrangement of 
chlorophyll. Can Vaucheria probably use carbon dioxide? 

284. Reproduction in Vaucheria. — Make an outline sketch of 
fruiting organs, if found. See if any filaments can be found with 
the contents massing or escaping at the tips. In some species 



TYPES OE CKYPTOGAMS; THALLOPHYTES 247 

zoospores are formed in this way, having their entire surface clothed 
with cilia. They are the largest motile cells known. In other spe- 
cies a portion of the filament is separated and cut of£ by a cell-wall. 
Such spores soon germinate and may be found in various stages of 
growth. They often serve for propagation through several genera- 
tions before spores are produced by fertilization. 

With a power of about 200 diameters sketch a portion of a fila- 
ment to show the form and location of chlorophyll. Sketch the 
fruiting organs in detail, if any can be found.^ 

Antheridia and oogonia are formed near together on the same 
filament. The antheridium is a cell forming the terminal portion 
of a short branch, which is rather slender, straight or curved. Its 
contents form numerous minute antherozoids, each with two cilia. 
The cilia can be seen only with great difficulty, if at all, but their 
presence is indicated by their active movements. 

The oogonium is a short, somewhat spheroidal branch separated 
by a cross-partition at the base. The cell-wall becomes ruptured at 
the tip, allowing the entrance of the antherozoids by which it is 
fertilized. After fertilization a cell-wall is formed about the oosphere, 
and it matures as an oospore and enters upon a period of rest. 

THE STUDY OF NITELLA 

285. Occurrence. — Nitella is a green plant growing attached to 
the bottom of ponds and streams, usually in shallow water. It is 
not common everywhere but is widely distributed. Chara is similar 
and may be used as a substitute but is more complicated. 

286. General Aspect. — With the naked eye and a magnify- 
ing glass note the general aspect of Nitella, the length of the stem- 
like portions, from the root-like parts to the tip, the length of some 
of the joints (internodes), the arrangement of leaf -like and branch- 
like portions. 

287. Protoplasm. — Examine the ceUs of stems or leaves under a 
low power. Select a vigorous cell of moderate size and examine 

1 Goebel states that the formation of the fruiting organs begins in the even- 
ing, is completed the next morning, and that fertilization takes place during 
the day between ten and four o'clock. 



248 



FOUNDATIONS OF BOTANY 



under a power of 200 or more diameters. Select the terminal cell 
of the leaf if Chara is used. The protoplasm is nearly colorless but 
usually contains bodies which can be seen moving in the current of 
protoplasm. The protoplasm will show 
normal activity at the temperature of a 
comfortable living room. By focusing, see 
if the current of protoplasm can be detected 
moving in more than one direction. 

Note the form and arrangement of the 
chlorophyll and any places lacking chloro- 
phyll, and see if you can tell whether the 
arrangement has any relation to the current' 
of protoplasm. With a low power trace the 
course in several cells. How many cells con- 
stitute each intern ode of Nitella 1 If Chara 
is used, internodes will be found to be 
covered with a layer of many corticating 
cells. Under a high power compare the 
general structure of node and internode and 
see if the attachment of leayes and branches 
can be clearly determined. Compare the tip 
of a leaf with the tip of a stem or branch 
if the material permits. Are the fruiting 
organs produced on the stems or the leaves? 
288. Antheridia. — The antheridia are 
globular bodies, bearing male fertilizing 
cells and becoming red at maturity (Fig. 
182). Eight cells compose the outer wall. 
They have radial lines indicating folds and 
join one another by irregular sutures. Note 
a round spot in the middle of each cell 
which marks the point of attachment within 
of the stalk on which anther ozoid-producing cells are borne. 

289. Oogonia. — The egg-shaped fruits, known as oogonia (Fig. 
182), are borne near the antheridia in monoecious species. Count 
the number of pointed cells which constitute the " crown " of the 
fruit. Does each tip consist of one or two short cells ? Examine 




Fig. 181. — End of a Main 
Shoot of Chara. (About 
natural size.) 



TYPES OF CRYPTOGAMS; THALLOPHYTES 



249 



the surface of the enveloping cells which enclose the spore. What 
is their number and form ? What is their relation to the cells form- 
ing the crown ? Focus so as to see the large egg-cell (oosphere or 
oospore) which constitutes the center of the fruit. Can you determine 
anything regarding its contents ? 

Search for young oogonia and if practicable describe and draw 
them in several stages of development. Their structure can be seen 
much more easily than that of the 
antheridia. Make drawings to illus- 
trate various details of structure. 

290. Characeae. — Mtella 
and Char a are the genera 
composing the group Chara- 
cece, a group of green algse 
differing widely from any 
others. They show in a won- 
derful manner simplicity of 
cell-structure with a high 
degree of organization. FiG.i82.-Partof aLeaf of rig. isi. 

1 p 1 (Considerably magnified.) 

Scarcely less wonderful are a,antheridium; o, oogonium. At the 
the care and precision with ^^g^* are a young antherldlum and 

which botanists have worked 

out their life history. As a study in evolution the Characece 
may be considered as representing the highest develop- 
ment attained along the line of filamentous green algse, 
which, while preserving their algal characteristics, are 
comparable in a remarkable degree with moss- and fern- 
plants and with seed-plants. Every cell in the plant has 
been accounted for and is understood in regard to origin, 
relationship, and function. With harmony of structure 
throughout, it has organs comparable to root, stem, and 
leaf in seed-plants, each with characteristic structure and 




250 



FOUNDATIONS OF BOTANY 



mode of growth. The stem has nodes and internodes. 
The stem increases by the growth of an apical cell, but 
growth in length depends chiefly on the elongation of each 
internodal cell instead of the multiplication of numerous 
internodal cells. 



THE STUDY OF EOCKWEEDi 

291. Occurrence. — The common rockweed is abundant every- 
where on rocks, between high and low tide, on the New England 
coast and southward. 

292. The Frond. — A plant of rockweed 
consists mostly of a growth which is some- 
what leaf-like, but, in fact, stem and leaf 
are not separately developed, and the growth 
is therefore called a thallus. This combined 
stem and leaf has many flat leathery 
branches which are buoyed up in the water 
by air-bladders. Cut one of the bladders 
open and note its form and appearance. Note 
whether they occur singly or how grouped. 
Note the prominent midrib running through- 
out the middle of each branch. Examine 
the swollen tips of some of the branches and 
note their peculiarities. Sketch a portion 
of a frond to show the characteristics so far 
noted. 

293. Reproduction. — Cut across through 
the middle of one of the swollen fruiting 
tips. Note the fruiting papillae (concep- 
tacles) as they appear in this section, and 
make a simple sketch to show their position. 

Select some plants with brighter colored 
tips and some less bright, if any difference 




Fig. 183. — Part of Thallus of 
a Rockweed (Fucus platy- 
carpus), natural size. The 
two uppermost branchlets 
are fertile. 



1 Fucus vesiculosus is the most available species, 
Others may be substituted. 



TYPES OF CEYPTOGAMS: THALLOPHYTES 



251 



can be detected. After making the 
microscopic examination which follows, 
note what correspondence of structure 
with color has been observed. Cut very- 
thin sections through fruiting tips from 
different plants, keeping those from each 
plant separate. Be sure that some of 
the cuts pass through the conceptacle as 
near the middle as possible. 

Examine with a power of about sixty 
diameters sections from different fronds, 
searching for one kind containing rather 
large egg-shaped cells and another con- 
taining bundles of numerous smaller 
sac-shaped cells. With a power of 200 
diameters study the details of the sec- 
tions. N'ote the character of the cells 
forming the surface of the frond, those 
of the inner structm^e, and those limit- 
ing the cavity of the conceptacle. In a 
conceptacle cut through the middle note 
the form of the orifice. Examine the 
slender hairs or filaments (parapkyses) 
which, arising at right angles, line the 
walls of the conceptacle. 

294. Oogonia and Antheridia. — In 
conceptacles containing egg-shaped cells 
(oogonia) note the form, 
mode of attachment (ses- 
sile or stalked), and dif- 
ferent stages of develop- 
ment. At maturity the 
contents are divided, 
forming eight oospheres; 
but not all can be seen 
at once 





Fig. 184. — Rockweed (Fucus). 
A, antheridia borne on branch- 
ing hairs, x 160 ; B, anthero- 
zoids from same, x 330. 




Fig. 185. — Kockweed (Fucus). 



some being: be- ^' ^^S^^i^^^' ^^s contents dividing into eight oospheres, 
X 160 ; B, an oosphere, escaped, surrounded by an 
neath the others. therozoids, x igo. 



252 



FOUNDATIONS OF BOTANY 



In conceptacles of the other kind examine the numerous small 
sac-shaped cells (antheridia). At maturity the contents of each 
divide to form numerous very minute motile antherozoids, each with 
two delicate hairs or cilia. Dissect, by picking and by friction under 

cover-glass, a bunch of 
antheridia and note 
the branching fila- 
ments upon which 
they are borne. 

Make drawings to 
illustrate the various 
points of structure. 

295. Number of 
Antherozoids required 
for Fertilization. — The 
bulk of an oosphere 
has been estimated 
equal to that of thirty 
thousand to sixty 
thousand antherozoids, 
but apparently an 
oosphere may be fer- 
tilized by only one 
antherozoid. Yet a 
large number swarm 
around each oosphere 
after both have 
escaped from the con- 
ceptacics, and often 
their movements are 
so active as to cause the rotation of the oosphere. The process of 
fertilization may be discerned in fresh material by squeezing 
oospheres and antherozoids from their respective conceptacles into 
a drop of water on a slide. In some species, as Fucus platycarpus 
(Fig. 186), antheridia and oogonia are found in the same 
conceptacle. 




Fig. 186. — Transverse Section of Conceptacle of ; 
Rockweed {Fucus platycarpus). (x about 35.) 

h, hairs ; a, antheridia ; o, oogonia. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 253 



THE STUDY OF NEMALION^ 

296. Occurrence. — Seven or eight species of Nemalion are known 
in the world, but only one i is widely diffused, being found in Europe 
and on the New England coast from Rhode Island northward. It 
grows in salt water attached to exposed rocks at low-water mark. 
Nemalion represents the largest of the groups of algse, nearly aU. of 
which live in salt water and have the characteristic color ; but a few 
live in fresh water. 

297. Color. — Fresh specimens or those properly dried for the 
herbarium show the color which is characteristic of the great group 
to which Nemalion belongs. Dried specimens of " Irish moss " 
(Chondrus) and many other species furnish good illustrations. There 
are many variations of shade and intensity. 

Place a piece of a fresh or dried specimen of some species in a 
beaker of fresh water over night or longer and note the color of the 
solution and of the treated specimen. Treat another piece similarly 
with alcohol. A few genera related to Nemalion grow in fresh 
water. What do you infer regarding their color ? 

298. Form and General Character. — Examine specimens of 
Nemalion and note the size, shape, mode of branching, nature, or 
consistency of their substance. Examine a fragment of the plant 
with a power of about sixty diameters and note how the structure 
differs from what it appears to be to the naked eye. Do cells appear 
more densely packed or differently colored at any points? 

299. Structure. — From a small portion of the plant cut thin 
longitudinal and transverse sections or pull it to pieces with needles 
so as to expose the inner portion. Place on a slide under a cover- 
glass in a drop of water. With a power of about 250 diameters or 
more examine the general structure of the frond, as shown by a slide 
prepared as above. Note the central portion (axis) of the frond as 
dissected out, consisting of long, slender, thread-like cells. Examine 
and draw the branching rows of cells which, radiating from the 
axis, form the surrounding outer structure of the frond. Note the 
tips of these branches and look for the fruiting organs and fruit 
(spores'). 

1 Nemalion multifidum,. 



254 



FOUNDATIONS OF BOTANY 



300. Organs for Repro- 
duction. — The fruiting 
organs are to be sought 
on the radiating branching 
filaments and are usually 
produced in great abun- 
dance during the summer. 
Various stages of develop- 
ment may be expected at 
a given time. The anther- 
ozoids are small spheres 
without cilia, non-motile, 
with a thin cell-wall. Look 
for cells in which they are 
formed (antheridid), occur- 
ring in groups at the tips 
of the branches. Compare 
these with the vegetative 
cells. 

301. spore -Production. 
— Look for spore-producing 
organs in various stages. 
In the young stage at the 
time of fertilization, an- 
therozoids, carried by cur- 
rents of water, may be 
found adhering. Note the 
shape of the tip (tricTiogyne) 
and the base (carpogonium), 
and find whether there is 
any partition separating 
them at this stage. Draw 
or describe a few later 
stages in development, and 
note the arrangement of 

the spores at maturity. Are they naked or enclosed in any sort of 
envelope ? Are they arranged in masses, chains, or otherwise ? 




B C 

Fig. 187. — Portions of Thallus of a Hed Alga 
(Chantransia). (Much magnified.) 

A, filaments with antheridia, a ; B, young recep- 
tive hair, or trichogyne, t ; C and D, successive 
stages in the growth of the clustered fruit,/. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 



255 



302. Other Florideae. — Nemalion represents one of the simplest 
modes of fruiting in the red algae. In others there is great variety in 
structure and great complication in the mode of fruiting. Some 
species of PolysipTionia (or Dasyd) may well be studied in compari- 
son with Nemalion and in further illustration of this important 
group.^ Understanding that a siphon, in algse, is a row of cells, end 
to end, study the structure of a plant of Poly- 
siphonia as illustrating its name. How many 
siphons are there? Do the main branches 
have any other cells covering the surface (cor- 
ticating cells) ? 

Note the tufts of repeatedly forking, one- 
siphoned filaments. 

303. Fruiting of Polysiphonia. — The anther- 
idia are to be sought on the branching fila- 
ments just mentioned. N'ote how they differ 
from those of Nemalion. The clustered fruits 
or cystocarps will be recognized as ovoid- @ 
globose or urn-shaped bodies attached 
externally to the frond. Note whether @ 
the group of spores is naked or otherwise, © 
whether the spores are produced singly 
or in chains ; how attached ; shape. 

Many Floridece have another kind of 
fruiting bodies, spores produced without 
fertilization, coordinate with the asexual 
spores of black mould (see Sect. 308). 
In Floridece such spores are usually 
found in fours and are called tetraspores. 

Are tetraspores usually found on separate plants ? 

In Polysiphonia the tetraspores appear to be formed in threes 
(tripartite^, the fourth being underneath the three. When found, 
describe their position and arrangement. 

304. Algae. — Diatom^ Oscillatoria, Pleurococcus, Spi- 
rogyra^ VaucJieria, Nitella, Fucus, Nemalion^ these eight 

1 It is desirable also to exhibit fresh or pressed specimens of various genera 
to show their general aspect. 




(i)« 



Fig. 188. 
^, spores of Nemalion (greatly 
magnified) ; B, portion of 
thallus of a red alga, Lejo- 
lisia, with tetraspores, t. 



256 FOUNDATIONS OE BOTANY 

plants which we have just studied, are types of several 
families of plants which together make the great group 
called Algce. Something of its importance in nature is 
indicated by these facts : The number of known species is 
about 12,000. In size, the individuals in various species 
range from a single cell of microscopic dimensions, as in 
Pleurococcus, to the giant kelp of California which reaches 
a length of more than 1000 feet. The form ranges from a 
simple spherical cell as in Pleurococcus to an extensive, 
branching cell in Vaucheria and its allies, specialized 
organs in the form of root, stem, leaf, air-bladder, and 
fruiting organs in Sargassum^ which is an ally of Fueus. 

The algse illustrate a series of modes of propagation 
from simple division in Oscillatoria to the union of two 
similar masses of protoplasm to form a spore in Spirogyra^ 
the direct fertilization of a germ-cell by motile anthero- 
zoids in Vaucheria, Nitella, Fucus, the indirect fertilization 
of fruiting cells by non-motile antherozoids in Nemalion. 
In allies of the latter there are more intricate variations of 
the same mode. 

The algse fall into five natural groups based primarily 
on the mode of fruiting. In most cases color is coordinate 
with class and may be relied upon as a superficial guide in 
grouping ; but there are a few exceptions, e.g., some fruit- 
ing like the red group are, nevertheless, green. 

The nutrition of the brown and the red algse is similar 
to that of the green algae, since the brown or red color 
merely conceals the green of the chlorophyll which is 
present in all and enables them all to take in and decom- 
pose carbon dioxide.^ 

1 See Murray's Introduction to the Study of Seaweeds, pp. 4-6. London, 
1895. 



TYPES or CRYPTOGAMS; THALLOPHYTES 257 

305. Classification of Types studied. 

DiATOMACE^. Yellowish. 

Diatoms. 
Cyanophyce^. Blue-green or some similar color. 

Oscillatoria. 
Chlorophyce^. Green. 

Pleurococcus, Spirogyra, 

Vaucheria, Nitella. 
Ph^ophyce^. Olive. 

Fucus. 
Floride^. Red. 

Nemalion. 

Polysiplionia. 

THE STUDY OF BLACK MOULD (RHIZOPUS NIGRICANS) 

306. Occurrence. — This mould maybe found in abundance on 
decaying fruits, such as tomatoes, apples, peaches, grapes, and cher- 
ries, or on decaying sweet potatoes or squashes. For class study it 
may most conveniently be obtained by putting pieces of wet bread 
on plates for a few days under bell-jars and leaving in a warm place 
until patches of the mould begin to appear. 

307. Examination with the Magnifying Glass. — Study some of 
the larger and more mature patches and some of the smaller ones. 
Note: 

(a) The slender, thread-like network with which the sm-face of 
the bread is covered. The threads are known as Tiyphce, the entire 
network is called the mycelium. 

(F) The delicate threads which rise at intervals from the myce- 
lium and are terminated by small globular objects. These little 
spheres are spore-cases. Compare some of the spore-cases with 
each other and notice what change of color marks their coming to 
maturity. 

308. Examination with the Microscope. — Sketch a portion of the 
untouched surface of the mould as seen (opaque) with a two-inch 
objective, then compare with Fig. 189. 



258 



FOUNDATIONS OF BOTANY 



Wet a bit of the mould, first with alcohol, then with water. 
Examine in water with the half-inch objective, and sketch a little of 
the mycelium, some of the spore-cases, and the thread-like stalks on 
which they are borne. Are these stalks and the mycelium filaments 
solid or tubular ? Are they one-celled or several-celled ? 

Mount some of the mature spore-cases in water, examine them 
with the highest obtainable power, and sketch the escaping spores. 




Fig. 189. 



■ Unicellular Mycelium of a Mould (Mucor Mucedo), sprung from a 
Single Spore. 



a, b, andc, branches for the production of spore-cases, showing various stages of 
maturity. (Considerably magnified.) 



Sow some of these spores on the surface of " hay-tea," made by 
boiling a handful of hay in just water enough to cover it and then 
straining through cloth or filtering through a paper filter. After 
from three to six hours examine a drop from the surface of the 
liquid with a medium power of the microscope (half-inch objective) 
to see how the development of hyphse from the spores begins. 
Sketch. 



TYPES OF CKYPTOGAMS; THAJLLOPHYTES 



259 



After about twenty-four hours examine another portion of the 
mould from the surface of the liquid and study the more fully 
developed mycelium. Sketch. 

309 . Zygospores . — Besides 
the spores just studied, zygo- 
spores are formed by conju- 
gation of the hyphse of the 
black moulds. It is not very 
easy to find these in process 
of formation, but the student 
may be able to gather from 
Fig. 190 the nature of the 
process by which they are 
formed, — a process which can- 
not fail to remind him of the 
conjugation of pond-scum. 

THE STUDY OF WHEAT 

KUST (PUCCINIA 

GRAMLN-IS) 

310. Occurrence. — Wheat 
rust is common on cultivated 
wheat and other grains, and 
also on many wild and culti- 
vated forage grasses. In fact, 
this or similar rusts occur on 
a very large number of grasses, 
and many species of such rusts 
are recognized, A rust may 
have one, two, or three kinds 
of spores, and when three occur one is known as the cluster-cup stage 
and the others as red rust and black rust, according to the usual 
approximate color of the spores. The rust called Puccinia graminis 
growing on wheat has its cluster-cup stage on the leaves of barberry 
in June. The spores from the cluster-cups are carried by the wind 
to the wheat, where they germinate and in a few days produce the 




'^::::>j 



Y'-^l 



•Formation of Zygospores in a 
Mould {Mucor Mucedo). 
1, threads in contact previous to conjuga- 
tion ; 2, cutting off of the conjugating 
cells, a, from the threads, 6 ; 3, a later 
stage of the process ; 4, ripe zygospore ; 5, 
germination of a zygospore and formation 
of a spore-case. (1-4 magnified 225 diam- 
eters, 5 magnified about 60 diameters.) 



260 



FOUNDATIONS OF BOTANY 



red rust. A little later the black spores appear, produced from the 
same mycelium. This growth is chiefly upon the stems and sheaths. 




Fig. 191, — Spore-Formation in Potato-Blight {Phytophthora infestans). 

A, a well-developed group of stalks, proceeding from a mass of mycelium inside 
the leaf and escaping through a stoma ; £, a young, unbranched stalk, h, 
hyphse of mycelium ; o, stoma ; s, spore. (Both figures greatly magnified, B 
more than A.) 

311. Cluster-Cup Stage. — Note with the naked eye and with a 
magnifying glass the appearance of the cluster-cups upon the bar- 
berry leaf. Fresh specimens should be used, if available. Note 
whether the leaf is changed in form or color in any part occupied 
by the fungus. Note the number of cups in a cluster, the position 
on the leaf (which surface?), the form and size, especially the height. 



TYPES OE CRYPTOGAMS ; THALLOPHYTES 261 

Are they straight or curved ? Describe the margin of the cup, the 
color without, and the color of the contents. 

With a power of 200 diameters or more examine some of the 
cells composing the cup and note the form, color, and nature of the 
surface. Draw. With the point of a needle or knife pick out a 
bit of the contents of the cup and examine as above. ISTote the 
characters as before and compare in detail with the cells of the cup. 
The cells within the cup are the spores. Can you tell how they are 
attached ? 

A thin section through the cup will show the mode of attachment 
and the relation of the spores to the cup. 

312. Examination of Red and Black Rust. — Under the magnify- 
ing glass examine the eruptions of spores (sori) on the wheat plant, 
some of red spores and some of black spores. The red spores are 
faded in dried specimens. Note the approximate size and shape 
and any other peculiarities. Prepare slides of each kind of spores 
and see if both can be found in one sorus. The spores may be 
taken from the host-plant on the point of a knife by picking rather 
deeply down into the sorus. Place the small quantity of spores so 




Fig. 192. —A Cliister-Cup of Anemone Rust {Puccinia fusca). (x 120.) 
s, chains of spores ; p, the covering or peridium of the cup ; h, hyphae. 

obtained in a drop of water on a slide, spread with dissecting needles 
and cover. Examine under a power of 200 or more diameters. 

The red spores (uredospores) have each a stalk from which they 
easily fall. They may be seen attached to their stalks if properly 



262 



FOUNDATIONS OF BOTANY 



prepared cross-sections through the sorus are available, especially if 
the material is fresh. Examine the spores and note the sha.pe, color, 
and surface. If the spores are shrunken, a drop of potash solution 
will restore the natural plumpness. Draw. Spore-measurements are 
important in determining species. The uredospores of Puccinia 
graminis may be distinguished from those of other species common 
f; on grasses by the greater proportionate 

length. 

The structm-e of the black spores 
(teleutospores) can be made out with- 
out difficulty. Some should be found 
attached at the base. N'ote the parts 
and the differences in color in different 
portions. Make careful drawings to 
show shape and structure of both kinds 
of spores. 

Boil a portion of a rust-injured plant 
in potash solution, pick it to pieces on 
a slide under the magnifier or dissect- 
ing microscope, use a cover-glass and 
examine the preparation for mycelium, 
using a high power. 

313. Cultivation on a Host-Plant. — 
If practicable, find some wheat or grass 
which has remained over winter with 
the black rust upon it. Tie a bunch 
of this to a barberry bush while the 
leaves are young or unexpanded. When 
the time arrives for the appearance of 
the cluster-cups, note whether they are any more abundant on this 
bush than on others. Are you sure that the rust you have is the 
one to which the barberry cluster-cups belong ? 




Fig. 193. — a Group of Spores 
of Wheat Rust {Puccinia 
graminis). (x about 440.) 
u, u, uredospores ; t, a teleu- 
tospore. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 263 



THE STUDY OF MICROSPH^RA 

314. Occurrence. — Species of Microsphoera and allied forms 
occur in late summer and fall on leaves of various herbaceous and 
woody plants. The growth is confined to the surfaces of the leaf 
(upper, lower, or both). Among the most available species are 
those which grow upon lilac, oak, grape, cherry, willow, and wild 
plants of the sunflower family. Some species are known to occur 
on only one host-plant, others occur on several or a large number, 
and the host-plants may belong to one or n\ore than one family. 

Besides Microsphcera there are about five other genera, any of 
which may be substituted or studied comparatively. They are dis- 
tinguished by the form of the appendages, together with the number 
of spore-sacs (asci) in each sac-receptacle or perithecium. 

The species of fungi which Microsphcera represents are called 
powdery mildews. 

With naked eye and magnifying glass examine the surface of a 
leaf bearing powdery mildew, l^ote which surface and what portion 
of the surface is occupied by the fungus, whether the occupied area 
is restricted or not, the color, and any other characters. 

315. Examination with the Microscope. — Place a small drop of 
water on the leaf where the fungus occurs, if possible where dark- 
colored specks occur among the mycelium. Pick from the leaf a 
portion of the fungus loosened by the water and place with a drop 
of water on a slide. Place a cover-glass over it. Examine under 
a power of about fifty diameters. The dark-colored specks will be 
seen as somewhat spherical bodies (perithecia). Note their structure 
and color and their appendages. Have the perithecia any regular 
way of opening? Note the length of the appendages as compared 
with the diameter of the perithecia ; also note the form of the tips 
and of the base, the color and any variation of color in different 
parts of the appendages. Keep the left hand on the focusing screw, 
and with the needle in the right hand press with gentle but varying 
stress upon the cover-glass to rupture the perithecia. Even with 
great care broken cover-glasses may result, but this pressure should 
force out the contents of the perithecia. Another method is to 
remove the slide from the microscope and, with a pencil rubber 



264 



FOUNDATIONS OF BOTANY 



— cap 



applied to the cover-glass, rupture the perithecia by gentle grinding 
between the cover and slide. Note the number and form of the 
spore-sacs (asci) expelled from each of several perithecia. Examine 

under a power of about 200 diam- 
eters and count the number of spores 
in the asci. Gentle pressure may 
make them more distinctly visible. 
Make drawings to illustrate the 
structural characters observed. 



THE STUDY OF AGARICUS 

316. Occurrence. — The common 
mushroom, A garicus campestris, 
grows in open fields and pastures 
in the United States and Europe. 
It is the mushroom most extensively 
cultivated for market, and if not 
found in the field it may be raised 
from " spawn " (mycelium), put up 
in the shape of bricks, and sold by 
seedsmen in the large cities. Those 
who make a specialty of selling it 
furnish directions for cultm^e free. 
A moderately warm cellar or base- 
ment makes an excellent winter 
garden for mushrooms. 

317. Structure of Mycelium. — 
Examine some of the spawn, or 
mycelium, with the magnifying glass 
and the low power of the microscope, 
and with a power of 200 diameters 
or more examine the individual 

hyphse which compose it. Are the hyphse united in cord-like strands 
or otherwise, or are they entirely separate ? Look for cross-partitions 
in the hyphse. Is there any peculiar structure to be found at these 
places ? Are the cross-partitions near together or widely separated ? 




Fig. 194. — A Mushroom {Agaricus 

melleus). 
my, mycelium ; c, c', c", young 

" buttons " ; st, stipe or stalk ; r, 

ring; S', gills. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 



265 





318. The Spore-Plant. — Search for indications of fruiting, and 
note the appearance of the " button mushrooms " in all available 
stages. Draw. See if at any stage up to maturity an outer envelope 
of tissue (yolva) can be found enclosing the entire fruiting body. 
If such be present, what becomes of it at maturity? If material is 
available, compare the species of Amanita (poisonous) in regard to this. 

Examine specimens in which the cap is expanding and see if 
there is another tissue forming a veil covering the under surface of 
the cap. If such be pres- 
ent, how is it attached '^ 
and what becomes of it? 

Take a fresh, well- 
expanded mushroom or 
toadstool. Remove the 
stalk, or stipe, close under 
the cap, or pileus, and lay 
the latter, gills down, on 
a piece of paper. Let it 
remain undisturbed for a 
few hours, or over night, 
so that the spores may 
fall upon the paper. Note 
carefully their color, also 
the form in which they 

are arranged on the paper. What determines this form ? Examine 
some of the spores under the highest available power of the micro- 
scope. Measure and draw. 

Describe the stipe. Is it a hollow tube or solid ? Does it taper ? 
l!^ote length, diameter, color. 

Describe the cap, or pileus, in regard to diameter, thickness, nature 
and color of the upper surface, also color below. 

Examine the plates, or gills, which compose the under portion of 
the pileus. Cut a complete pileus and stipe, through the center, and 
draw an outline to show the shape, noting particularly how the gills 
are attached. What is the color of the gills ? 

319. Origin of Spores. — Make a cross-section of one of the gills, 
and with a magnifying power of about 200 diameters examine the 



B 

Fig. 195. — Portions of Gills of 

V a Fungus {Agaricus). 
A, slightly magnified ; B, one 
of the parts of A, more mag- 
nified, hym, hymenium ; h, 
central layer. 



266 



FOUNDATIONS OF BOTANY 



fruiting cells (basidia) which project at right angles to the gill and 
bear the spores. At how many points (sterigmatd) on each basidium 
are spores attached ? Draw a basidium, preferably one from which 
the spores have not yet fallen. 



THE STUDY OF YEAST (SACCHAROMYCES CEREVISI^E) 

320. Growth of Yeast in Dilute Syrup, — Mix about an eighth of 
a cake of compressed yeast with about a teaspoonful of water and 
stir until a smooth, thin mixture is formed. Add this to about half 

a pint of water in which a table- 
spoonful of molasses has been 
dissolved. Place this mixture in 
a wide-mouthed bottle which holds 
one or one and a half pints, stop- 
per very loosely ^ and set aside for 
from twelve to twenty-four hours 
in a place in which the temper- 
ature will be from 70 to 90 degrees. 
Watch the liquid meantime and 
note : 

(a) The rise of bubbles of gas 
in the liquid. 

(&) The increasing muddiness 
of the liquid, a considerable sedi- 
ment usually collecting at the end 
of the time mentioned. 

(c) The effect of cooling off the 
contents of the bottle by immers- 
ing it in broken ice if convenient, 
or, if this is not practicable, by 
standing it for half an hour in a pail of the coldest water obtainable, 
or leaving it for an hour in a refrigerator, afterwards warming the 
liquid again. 

(c?) The effect of shutting out light from the contents of the 
bottle by covering it with a tight box or large tin can. 

1 If the cork is crowded into the neck with any considerable force, pressure 
of gas and an explosion may result. 




Fig. 196. — Part of the Preceding Figure. 
(X about 300.) 

C, layer of cells immediately under the 
hymenium ; s, s', s", three successive 
stages in growth of spores. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 267 

(e) The result of filling a test-tube or a very small bottle with 
some of the syrup-and-yeast mixture, from which gas-bubbles are 
freely rising, and immersing the small bottle up to the top of the 
neck for fifteen minutes in boiling water. Allow this bottle to 
stand in a warm place for some hours after the exposure to hot 
water. What has happened to the yeast-plants? 

(/) The behavior of a lighted match lowered into the air space 
above the liquid in the large bottle, after the latter has been standing 
imdisturbed in a warm place for an hour or more. 

(^) The smell of the liquid and its taste. 

321. Microscopical Examination of the Sediment.^ — Using a very 
slender glass tube as a pipette, take up a drop or two of the liquid 
and the upper layer of the sediment and place on a glass slide, cover 
with a very thin cover-glass and examine with the highest power 
that the microscope affords. 

Note: 

(a) The general shape of the cells. 

(b) Their granular contents. 

(c) The clear spot, or vacuole, seen in many of the cells. 
Sketch some of the groups and compare the sketches with 

Fig. 197. 

Run in a little iodine solution under one edge of the cover-glass, 
at the same time touching a bit of blotting paper to the opposite 
edge, and notice the color of the stained cells. Do they contain starch ? 

Place some vigorously growing yeast on a slide under a cover- 
glass and run in a little eosin solution or magenta solution. Note 
the proportion of cells which stain at first and the time required for 
others to stain. Repeat with yeast which has been placed in a slen- 
der test-tube and held for two or three minutes in a cup of boiling 
water. 

With a very small cover-glass, not more than three-eighths of an 
inch in diameter, it may be found possible by laying a few bits of 
blotting paper or cardboard on the cover-glass and pressing it against 
the slide to burst some of the stained cells and thus show their thin, 
colorless cell-walls and their semi-fluid contents, protoplasm, nearly 
colorless in its natural condition but now stained by the iodine. 
1 See Huxley and Martin's Biology, under Torula. 



268 



FOUNDATIONS OE BOTANY 



EXPERIMENT XXXIX 



Can Yeast grow in Pure Water or in Pure Syrup ? — Put a bit of 

compressed yeast of about the size of a grain of wheat in about four 
fluid ounces of distilled water, and another bit of about the same size 
in four fluid ounces of 10 per cent solution of rock candy in distilled 
water ; place both preparations in a warm place, allow to remain for 
twenty-four hours, and examine for evidence of the growth of the 
yeast added to each. 

322. Size, Form, and Structure of the Yeast-Cell. — The student 
has discovered by his own observations with the microscope that the 
yeast-cell is a very minute object, — much smaller than most of the 
vegetable cells which he has hitherto examined. The average diam- 
eter of a yeast-cell is about goViy 
of an inch, but they vary greatly 
both ways from the average size. 

The general form of most of 
the cells of ordinary yeast is some- 
what egg-shaped. The structure 
is extremely simple, consisting of 
a thin cell-wall, which is wholly 
destitute of markings, and a more 
or less granular semi-fluid proto- 
plasm, sometimes containing a 
portion of clearer liquid, the vacu- 
ole, well shown in the larger cells 
of Fig. 197.1 

323. Substances which compose the Yeast-Cell. — The cell- wall is 
composed mostly of cellulose; the protoplasm consists largely of 
water, together with considerable portions of a proteid substance,^ 

1 This is not the ordinary commercial yeast. 

2 It may be found troublesome to apply tests to the yeast-cell on the slide, 
under the cover-glass. Testing a yeast cake is not of much value, unless it 
may be assumed that compressed yeast contains little foreign matter and con- 
sists mostly of yeast-cells. Still the test is worth making. Millon's reagent 
does not work well, but the red or maroon color which constitutes a good test 
for proteids is readily obtained by mixing a teaspoonful of granulated sugar 
with enough strong sulphuric acid to barely moisten the sugar throughout, 
and then, as quickly as possible, mixing a bit of yeast cake with the acid and 




Fig. 197. — Yeast {Saccharomyces ellip- 
soideus) budding actively. 

A, a single cell ; B, group of two budding 
cells ; C, a large group ; b, buds. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 269 

some fat, and very minute portions of sulphur, phosphorus, potash, 
magnesia, and lime. It is destitute of chlorophyll, as would be 
inferred from its lack of green color, and contains no starch. 

324. Food of the Yeast-Cell ; Fermentation. — The diluted molasses 
in which the yeast was grown in Exp. XXXIX contained all the 
mineral substances mentioned in Sect. 323, together with sugar, 
proteid materials, and water. The addition of a little nitrate of 
ammonium would probably have aided the growth of the yeast in 
this experiment, by supplying more abundantly the elements out 
of which the yeast constructs its proteid cell-contents. A great deal 
of sugar disappears during the growth of the yeast.^ Most of the 
sugar destroyed is changed into carbon dioxide (which the student 
saw rising through the liquid in bubbles) and alcohol, which can 
be separated from the liquid by simple means. The process 
of breaking up weak syrup into carbon dioxide and alcohol by 
aid of yeast is one kind of fermentation; it is of great practical 
importance in bread-making and in the manufacture of alcohol. 
Since grape juice, sweet cider, molasses and water, and similar 
liquids, when merely exposed to the air soon begin to ferment and 
are then found to contain growing yeast, it is concluded that dried 
yeast-cells, in the form of dust, must be everywhere present in 
ordinary air. 

325. Yeast a Plant ; a Saprophjrte. — The yeast-cell is known 
to be a plant, and not an animal, from the fact of its producing 
a coating of cellulose around its protoplasmic contents and from 
the fact that it can produce proteids out of substances from which 
animals could not produce them.^ 

On the other hand, yeast cannot live wholly on carbon dioxide, 
nitrates, water, and other mineral substances, as ordinary green 
plants can. It gives off no oxygen, but only carbonic acid gas, and 
is therefore to be classed with the saprophytes, like the Indian pipe, 
among flowering plants (Sect. 180). 

sugar. A comparative experiment may be made at the same time with some 
other familiar proteid substance, e.g., wheat-germ meal. 

1 The sugar contained in molasses is partly cane sugar and partly grape 
sugar. Only the latter is detected by the addition of Fehling's solution. 
Both kinds are destroyed during the process of fermentation. 

2 For example, tartrate of ammonia. 



270 FOUNDATIONS OF BOTANY 

326. Multiplication of Yeast. — It is worth while to notice the 
fact that yeast is one of the few cryptogams which have for ages 
been largely cultivated for economic purposes. Very recently yeast 
producing has become a definite art, and the cakes of compressed 
yeast so commonly sold afford only one instance of the success 
that has been attained in this process. While yeast-cells are under 
favorable conditions for growth, they multiply with very great 
rapidity. Little protrusions are formed at some portion of the 
cell-wall, as the thumb of a mitten might be formed by a gradual 
outgrowth from the main portion. Soon a partition of cellulose 
is constructed, which shuts off the newly formed outgrowth, making 
it into a separate cell, and this in turn may give rise to others, 
while meantime the original cell may have thrown out other off- 
shoots. The whole process is called reproduction ty budding. It is 
often possible to trace at a glance the history of a group of cells, 
the oldest and largest cell being somewhere near the middle of the 
group and the youngest and smallest members being situated around 
the outside. Less frequently the mode of reproduction is by means 
of spores, new cells (usually four in number), formed inside one of 
the older cells (ascus). At length the old cell-wall bursts, and the 
spores are set free, to begin an independent existence of their own. 

In examining the yeast-cell the student has been making the 
acquaintance of plant life reduced almost to its lowest terms. The 
very simplest plants consist, like the slime moulds, of a speck of 
jelly-like protoplasm. Yeast is more complex, from the fact that its 
protoplasm is surrounded by an envelope of cellulose, the cell-wall. 

THE STUDY OF PHYSCIA 

327. Occurrence. — Physcia is one of the commonest lichens. It 
grows attached to the bark of various trees. 

328. The Thallus. — Physcia consists chiefly of an irregularly 
expanded growth somewhat leaf-like in texture. It is best to be wet 
for study. Is it separable from the bark to which it is attached or 
is it combined with it (incrusted) ? Describe the general outline of 
the margin, the general color, and any special variations of color 
above, also below, How is the thallus attached to the bark ? 



TYPES OF CRYPTOGAMS; THALLOPHYTES 



271 



329. The Fruit. — Look for small lance-shaped disks seated upon 
the thallus. Note the approximate sizes and color within and 
without. These disks are called apothecia. IsTote the very minute 
black specks (spermogones) which are scattered in the surface of 
the thallus. Pick one from the thallus, with as little of the thallus 
as possible, and examine under high power. It may be macerated 
in a drop of potash solution and crushed under the cover-glass. If 
the contents are not easily 
defined, they may then be 
made more opaque by a drop 
of acetic acid or a stain. The 
minute colorless bodies con- 
tained in the spermogones are 





Fig, 198, — A Lichen (Xanthoria). 
(Natural size.) 



Fig. 199. — a Lichen {Usnea). 
(Natural size.) 



called spermatia. Their office in Physcia is obscm^e, but in a few 
lichens they are thought to unite with a trichogyiie cell, as in the red 
algse.i N'ote the minute, powdery masses (soredia) on the surface 
of the thallus. Macerate if necessary under the cover-glass and 
examine under a high power. Compare with the structure of the 
thallus as seen in cross-section. (See next paragraph.) These soredia 
easily become detached and develop into new plants. 

Prepare for sectioning by imbedding a small portion of the 
thallus with an apothecium in a piece of pith or by any suitable 
device for sectioning, and cut thin sections of thallus and fruit. 

1 This, however, is doubtful. See Strasburger, Noll, Schenk, and 
Schimper's Text-Book of Botany, p. 380. 



272 



FOUNDATIONS OF BOTANY 



330. Examination of the Thallus. — The thallus of Physcia as seen 
in cross-section will be found to consist of four layers, the upper 
cortical, gonidial, medullary, and the lower cortical. The cortical 
layers will be seen to serve for protection, answering the purpose of 
an epidermis or bark. -The cells which compose them make what 
is called a false parenchyma, — resembling parenchyma in form but 

as to origin being trans 

'.Of 



formed fungal hyphse. 
iN'ote the form of the 
hyphse composing the 
medullary layer. Are 
there any cross-parti- 
tions? Do any cells 
appear circular, and if 
so, what is the explana- 
tion? The upper por- 
tion of the cortical 
layer, having green 
cells intermixed, con- 
stitutes the gonidial 
layer. Why should the 
green cells be at the 
upper part of the med- 
ullary layer ? Can you 
detect any connection 
between the green cells 
and the hyphse ? Do 
these green cells re- 
semble any cells pre- 
viously studied ? 
Make a diagram to show the structure of the thallus. 
What arrangement of layers would you expect to find in a lichen 
thallus, upright or suspended? Compare the arrangement in the 
fruit-body (apothecium'), describe, and sketch. How does the layer 
of cells beneath the spore-sacs resemble the cortical layer ? All but 
these two layers may be considered as part of the thallus. To make 
out the details of the fruit, the section must be very thin. 




Fig. 200. — Transverse Section through Thallus 
of a Lichen (Stictafuliginosa). (x 500.) 

c, cortical or epidermal layer ; g, gonidia ; h, hyphte. 



TYPES OF CRYPTOGAMS; THALLOPHYTES 273 

Examine the spore-sacs (asci) and look for spores in different stages 
of formation. How many spores are found in each ascus ? What other 
bodies occur among the asci? Draw these, also asci and spores. 

331. Lichens. — Lichens were formerly supposed to be 
a distinct class of plants, and it is only about thirty years 
since their real nature began to be understood. A lichen 
is now known to be a combination of two plants. The 
green cells, called the gonidia^ belong to some species of 
alga, and the remainder, the larger portion of the growth, 
is a fungus parasitic upon that alga. The groups of 
lichens correspond in structure to certain groups of fungi, 
but the genera are sufQciently distinct so that lichens are 
best considered by themselves for purposes of study and 
classification. 

The relation of the fungus and its algal host is not 
that of destructive parasitism, but rather a mutual rela- 
tion {symbiosis) in which both fungus and alga may have 
a vigorous growth. The relationship has been investi- 
gated in various ways, and it has been found that, while 
the alga may grow independent of the fungus, the germi- 
nating fungus spores can grow only to a limited extent if 
deprived of the algal host; but if supplied naturally or 
artificially with the proper alga they make a normal 
growth. 

The same alga may serve as gonidia to a number of 
'lichens, often of very different form, and while the num- 
ber of lichens reaches into the thousands, the number of 
algse known to serve as gonidia is quite small. 

Lichens are widely distributed in all zones but flourish 
particularly in northern regions where other vegetation is 
scanty. Some were formerly important as sources of 



274 rOUNDATIONS OF BOTANY 

dyes. " Iceland moss " is a lichen used for food, and a 
finely branching form, growing in extensive mats on the 
soil, serves as food for the reindeer and is known as 
" reindeer moss." 

Most lichens grow on the bark of trees, on rocks, or soil 
where they have little moisture except during rainfall, 
but some grow where they are constantly wet. Some of 
the latter are gelatinous. Most of the conspicuous lichens 
are foliaceous or else have a thallus composed of branch- 
ing, cylindrical, thread-like portions. But many species, 
often less conspicuous, are crustaceous, growing as if 
they formed part of the bark or rock to which they are 
attached. 

332. Fungi. — The yeasts, moulds, rusts, mildews, and 
mushrooms represent an immense group of plants of which 
about forty-five thousand species are now known in the 
world. They range from the very simple to quite com- 
plex forms, growing as saprophytes or parasites under a 
great variety of conditions. Their structure and life 
history are so varied as to constitute a long series of divi- 
sions and subdivisions.^ Chlorophyll is absent from fungi, 
and they are destitute of starch, but produce a kind of 
cellulose which appears to differ chemically from that of 
other plants. Unable to build up their tissues from car- 
bonic acid gas, water, and other mineral matters, they are 
to be classed, with animals, as consumers rather than as 
producers, acting on the whole to diminish rather than to 
increase the total amount of organic material on the earth. 



1 See Strasburger, Noll, Schenk, and Schimper's Text-Book of Botany, 
pp. 340-381 incl., also Potter and Warming's Systematic Botany, p. 1, and 
Engler's Syllabus der Pflanzenfamilien, Berlin, 1898, pp. 25-47. 



TYPES OF CRYPTOGAMS ; THALLOPHYTES 275 

333. Occurrence and Mode of Life of Fungi. — Among 
the most important cryptogamous plants are those which, 
like the bacteria of consumption, of diphtheria, of typhoid 
fever, or of cholera, produce disease in man or in the 
lower animals. The subclass which includes these plants 
is known by the name Bacteria. Bacteria are now classed 
by some as a separate group, lower than fungi. Some of 
the most notable characteristics of these plants are their 
extreme minuteness and their extraordinary power of 
multiplication. Many bacteria are on the whole highly 
useful to man, as is the case with those which produce 
decay in the tissues of dead plants or animals, since these 
substances would, if it were not for the destructive action 
of the bacteria of putrefaction and fermentation, remain 
indefinitely after death to cumber the earth and lock up 
proteid and other food needed by new organisms. 

The mushrooms and their allies include about one-fourth 
of the fungi. Some, such as the " dry-rot " fungus, mis- 
takenly so called, cause great destruction to living and 
dead tree trunks and timber in economic use. The com- 
mon mushroom, Agaricus campestris, is the most important 
edible species. Probably five hundred kinds can be eaten, 
but only a few are good food, and even these contain but little 
nutriment. Some species are dangerous, and a few are deadly 
poisons. The puff balls are a small group allied to the mush- 
rooms. Most of them are edible and of good quality. 

The mildews (Microsphoera, etc.) and the "black-knot" 
of the plum trees are of a group which likewise includes 
about one-fourth of the fungi. A considerable number 
are parasites, injurious to vegetation, while thousands of 
others grow on dead leaves, twigs, etc. 



276 FOUNDATIONS OF BOTANY 

The "rust" of wheat and the "smut" of corn repre- 
sent groups numbering only a few hundreds of species, 
which are very important because they are all parasites 
on living plants, many on our most important economic 
plants. 

Fig. 191, representing another small group of destruc- 
tive parasites, shows clearly how a parasitic fungus grows 
from a spore which has found lodgment in the tissues of 
a leaf and pushes out stalks through the stomata to dis- 
tribute its spores. 



CHAPTER XXI 



TYPES OF CRYPTOGAMS; BRYOPHYTES 



mr 



334. The Group Bryophytes. — Under this head are 
classed the liverworts and the mosses. Both of these 
classes consist of plants a good deal more highly organized 
than the thallophytes. 
Bryophytes have no 
true roots, but they 
have organs which 
perform the work of 
roots. Some of them 
have leaves (Fig. 206), 
while others have 
none (Fig. 2 01). 
Fibro -vascular bun- 
dles are wanting. The 
physiological division 
of labor is carried 
pretty far among all 
the bryophytes. They 
have special appara- 
tus lor absorbing Fig. 201.— Part of Male Tlmllus of a Liverwort 
water and sometimes (Marchantia dlsjuncta). (Enlarged.) 

f, n , • • ■ fnr, male receptacle. 

lor conducting it 

through the stem; stomata are often present and some- 
times highly developed. There are chlorophyll bodies, 
often arranged in cells extremely well situated for acting 

277 




278 



FOUNDATIONS OF BOTANY 



on the carbon dioxide gas which the plant absorbs, that is, 
arranged about rather large air chambers. 

Reproduction is of two kinds, sexual and asexual, and 
the organs by which it is carried on are complicated and 
highly organized. An alternation of generations occurs, 
that is, the life history of any species embraces two forms : 
a sexual generation^ which produces two kinds of cells that 

by their union give 
rise to a new plant ; 
the asexual genera- 
tion^ which multiplies 
freely by means of 
special cells known 
as spores. 




Fig. 202. —Part of Female Thallus of 
M. disjuncta. (Enlarged.) 

fr, female receptacle ; c, cups with gemmae. 



THE STUDY OF 
MARCHANTIA 



335. Occurrence. — 

Marchantia grows on soil 
or rocks in damp shaded places and is widely distributed. 

336. The Thallus. — In general form the thallus bears some resem- 
blance to that of some of the lichens, as Parmelia, but is plainly 
different in color, mode of branching, and internal structure under 
the microscope. Under the microscope (see below) the individual 
cells maybe compared with those of the medullary layer in Physcia. 

N'ote the color and general shape of the thallus and study care- 
fully the mode of branching. The origin of the growing cells is at 
the tip, but cells so originating afterward multiply more rapidly, so 
that the tip comes to be in a notch. 

Viewing the thallus as an opaque object, note the diamond-shaped 
network on the upper surface and the dot-like circle in the middle 
of each diamond. 

Examine the under surface for (1) rhizoids and (2) scales. 



TYPES OF CKYPTOGAMS; BRYOPHYTES 



279 




Fig. 203. — Section through Anther- 
idial Receptacle of Alarchantia. 
(Magnified.) 

a, antheridium. 



337. Internal Structure. — Cut thin cross-sections of the thallus 
in the same way as for Physcia, making some pass through the cir- 
cular dots mentioned above. Exam- 
ine under a high power and note the 
different kinds and layers of cells 
composing the thallus. ^ote the 
character of the cells forming the 
upper and lower surfaces. Describe 
the cells which are next above those 
of the lower epidermis, their shape, 
color of contents, approximate num- 
ber of horizontal rows. Have they 
any evident intercellular spaces ? Find 
cells connecting these with the upper 
epidermis and constituting the net- 
work of lines seen on the surface of 
the thallus. Note the air cavity 

bounded by these lines and the loose cells which occupy it in part. 
What is the color of their contents ? How are they attached, and 
how arranged? Can you discover any 
opening through the epidermis? If so, 
describe it. 

Make drawings to illustrate the details 
of structure observed. 

338. Gemmae. — Look for a thallus 
bearing little green cups formed of its 
own substance. Describe the contents 
of the cup. The bodies are called gemmce. 
They originate by vegetative growth alone 
and when detached may grow into new 
plants. 

339. Fruiting Organs. — Look for thalli 
bearing stalks with umbrella-like expan- 
sions. The umbrellas are of two kinds, 
one disk-like with crenate points (how 
many ?) and the other has rays (how many ?) elongated and curving 
downward. Is there any difference in the height of the two kinds ? 



az 




Fig. 204. — Sectional View of 
an Antheridium of Mar- 
chantia. 

a, antheridium ; az, anthero- 
zoids, X 700. 



280 



FOUNDATIONS OF BOTANY 



Do both occur on the same thallus ? On what part of the thallus 
do they occur, and do they differ in this respect ? 

340. Antheridia. — The antheridia are formed as outgrowths 
from the upper surface of the crenate receptacle, but by further 
growth of the receptacle they become imbedded. They should be 
examined under a high power and sketched m outline. The anther- 
idium produces numerous motile antherozoids, each with two cilia. 

341. Archegonia and Sporophytes. — The receptacle w^ith recurved 
rays bears the archegonia. Note whether they oct)ur above or below 
and in what relation to the rays. How are the archegonia protected? 

Note the cells which surround 
the central canal and form the 
elongated neck of the archego- 
nium. Does the archegonium 
open upward or downward ? At 
the base look for the germ-cell. 

The antherozoids enter the 
central canal and penetrating 
to the egg-cell fertilize it, after 
which it begins to divide and 
grows into a sporophyte. In the 
older specimens, therefore, the 
sporophytes will be found more 
or less developed. The archegonium remains upon the tip of the 
sporophytes. The mature sporophyte contains the spores and also 
peculiar elongated tapering threads with spiral thickenings. These 
are called elaters. 




Fig. 205. — Sectional View of Female 
Beceptacle of Marchantla. (x 5.) 



342. Hepaticae. — Marchantia represents only a small 
division of the Hepaticoe^ and is not typical of the larger 
number of species. In spite of this it is chosen for study, 
because it is widely distributed and more available for 
study than most others. In most species the fruit lasts 
but a little vrhile and good material is hard to obtain. In 
Marchantia the fruiting organs are abundant, more gradual 
in their development, and more persistent. Marchantia and 



TYPES OF CRYPTOGAMS; BRYOPHYTES 281 

its allies consist chiefly of the thallus in the vegetative con- 
dition, while the greater number of Hepaticse have a stem 
and leaves. Thus they approach closely to the mosses. 
But mosses usually have leaves on all sides of the stem, 
while the leaves of Hepaticse are two-ranked, spreading 
laterally, with sometimes a third row of leaves or scales 
underneath. The leaves of mosses usually have more than 
one layer of cells in some part, but the leaves of the leafy 
Hepaticse have but one layer of cells throughout. The 
forms of the leaves are often very curious and interesting. 
The sporophyte of most mosses consists of a capsule with 
a lid, while in the leafy Hepaticae the capsule usually 
opens by splitting longitudinally into two to four valves. 

Different species of Hepaticse grow on damp soil, rocks, 
and the bark of trees. Many are capable of enduring 
drought and reviving with moisture. 

THE STUDY OF PIGEON-WHEAT MOSS 
{POLYTRICHUM COMMUNE) 

343. Occurrence. — This moss is widely distributed over the sur- 
face of the earth, and some of its relatives are among the best 
known mosses of the northern United States. Here it grows 
commonly in dry pastures or on hillsides, not usually in densely 
shaded situations. 

344. Form, Size, and General Characters. — Study several speci- 
mens which have been pulled up with root-hairs. Note the size, 
general form, color, and texture of all the parts of the plants exam- 
ined. Some of them probably bear spore-capsules or sporophytes like 
those shown in Fig. 206, while others are without them. Sketch one 
plant of each kind, about natm-al size. 

What difference is noticeable between the appearance of the 
leaves in those plants which have spore-capsules and those which 
have none ? Why is this ? 



282 



rOUNDATIONS OF BOTANY 



In some specimens the stem may be found, at a height of an inch ] 
or more above the roots, to bear a conical, basket-shaped enlargement, , 




EiG. 206. — A Moss, Catharinea. 

The sporophytes of this moss are usually rather more slender than 
here represented. 



TYPES OF CRYPTOGAMS; BRYOPHYTES 



283 



out of the center of which a younger portion of the stem seems to 
proceed ; and this younger portion may in turn end in a similar 
enlargement, from which a still younger part proceeds. 

IsTote the difference in general appearance between the leaves of 
those plants which have just been removed from the moist collecting- 
box and those which have been lying for half an hour on the table. 
Study the leaves in both cases with the magnifying glass in order to 
find out what has happened to them. Of what use to the plant is 
this change ? Put some of the partially dried leaves in water, in a 




prim 



Fig. 207. — Protonema of a Moss. 

prim, primary shoot ; li, a young root-liair ; pi, young moss-plant ; 
hr, branches of primary shoot. 

cell on a microscope slide, cover, place under the lowest power of 
the microscope, and examine at intervals of ten or fifteen minutes. 
Finally sketch a single leaf. 

345. Minute Structure of the Leaf and Stem. — The cellular 
structure of the pigeon-wheat moss is not nearly as simple and con- 
venient for microscopical study as is* that of the smaller mosses, many 
of which have leaves composed, over a large part of their surfaces, 
of but a single layer of cells, as shown in Fig. 209. If any detailed 
study of the structure of a moss is to be made, it will, therefore, be 
better for the student to provide himself with specimens of almost 



284 



FOUNDATIONS OF BOTANY 



any of the smaller genera, ^ and 
work out what he can in regard 
to their minute anatomy. 




Fig. 208. —The Antheridium 
of a Moss (Funaria) and its 
Contents. 

a, antheridium ; b, escaping 
antherozoids, x 350 ; c, a sin- 
gle antherozoid of another 
moss, X 800. 




Fig. 209.— Portions of Fertile Plant 
of a Moss (Funaria). 

A, longitudinal section of summit Of 
plant, xlOO; a, archegonia; I, 
leaves ; £, an archegonium, x 550 ; 
e, enlarged ventral portion with 
central cell ; n, neck ; m, mouth. 



346. Sporophytes. — That part of the reproductive apparatus of 
a common moss which is most apparent at a glance is the sporophyte 
or spore-capsule (Fig. 206). This is covered, until it reaches maturity, 
with a hood which is easily detached. Remove the hood from one 

1 As Mnium or Bryum. 



TYPES OF CRYPTOGAMS; BRYOPHYTES 285 

of the capsules, examine with a magnifying glass, and sketch it. 
Note the character of the material of which its outer layer is 
composed. 

Sketch the uncovered capsule as seen through the magnifying 
glass, noting the little knob at its base and the circular lid. 

Pry off this lid, remove some of the mass of spores from the 
interior of the capsule, observe their color as seen in bulk through 
the magnifying glass, then mount in water, examine with the high- 
est obtainable power of the microscope, and sketch them. These 
spores, if sown on moist earth, will each develop into a slender, 
branched organism, consisting, like pond-scum, of single rows of 
cells (Fig. 207) called the protonema. 

347. Other Reproductive Apparatus. — The student cannot, with- 
out spending a good deal of time and making himself expert in the 
examination of mosses, trace out for himself the whole story of the 
reproduction of any moss. It is sufficient here to give an outline of 
the process. The protonema develops buds, one of which is shown 
in Fig. 207, and the bud grows into an ordinary moss plant. This 
plant, in the case of the pigeon-wheat moss, bears organs of a some- 
what flower-like nature, which contain either antheridia (Fig. 208), 
organs which produce fertilizing cells called antherozoids, or arclie- 
gonia (Fig. 209), organs which produce egg-cells, but in this moss 
antheridia and archegonia are not produced in the same " moss- 
flower." The plants therefore correspond to dioecious ones among 
flowering plants. 

After the fertilization of the egg-cell, by the penetration of 
antherozoids to the bottom of the flask-shaped archegonium, the 
development of the egg-cell into sporopliyte begins ; the latter rises 
as a slender stalk, while the upper part of the archegonium is 
carried with it and persists for a time as the hood or calyptra. 



CHAPTER XXII 
TYPES OF CRYPTOGAMS; PTERIDOPHYTES 

348. The Group Pteridophytes. — Under this head are 
classed the ferns, the scouring-rushes, and the club-mosses. 
They are the most highly organized of cryptogams, having 
true roots, and often well-developed stems and leaves. 

THE STUDY OF A FEE^i 

349. Conditions of Growth. — If the specimens studied were col- 
lected by the class, the collectors should report exactly in regard to 
the soil and exposure in which the plants were found growing. Do 
any ferns occur in surroundings decidedly different from these? 
What kind of treatment do ferns need in house culture? 

350. The Underground Portion. — Dig up the entire underground 
portion of a plant of ladyfern. Note the color, size, shape, and 
appendages of the rootstock. If any are at hand which were col- 
lected in their late winter or early spring condition, examine into 
the way in which the leafy parts of the coming season originate 
from the rootstock, and note their peculiar shape (Fig. 210, A). 
This kind of vernation (Sect. 136) is decidedly characteristic of ferns. 
Observe the number and distribution of the roots along the rootstock. 
Bring out all these points in a sketch. 

1 The outline here given applies exactly only to Asplenium filix-foemina. 
Any species of Asplenium or of Aspidium is just as well adapted for study. 
Cystopteris is excellent, but the indusium is hard to find. Polypodiufn vul- 
gare is a simple and generally accessible form, but has no indusium. Pteris 
aquilina is of world-wide distribution, but differs in habit from most of our 
ferns. The teacher who wishes to go into detail in regard to the gross anat- 
omy or the histology of ferns as exemplified in P^ens will find a careful study 
of it in Huxley and Martin's Biology, or a fully illustrated account in Sedg- 
wick and Wilson's Biology. 

286 



TYPES OF CRYPTOGAMS; PTERIDOPHYTES 287 

351. The Frond. — Fern leaves are technically known as fronds. 
Observe how these arise directly from the rootstock. 

Make a somewhat reduced drawing of the entire frond, which 
consists of a slender axis, the rhacMs, along which are distributed 
many leaflets or pinnce, each composed of many pinnules. Draw the 
under side of one of the pinnae, from near the middle of the frond, 
enlarged to two or three times its natural size, as seen through the 
magnifying glass. 'Note just how each pinnule is attached to its 
secondary rhachis. 

Examine the under side of one of the pinnules (viewed as an 
opaque object without cover-glass) with the lowest power of the 
microscope, and note : 

(a) The "fruit-dots" or sori (Fig. 210, B) (already seen with the 
magnifying glass, but now much more clearly shown). 

(&) The membranous covering or indusium of each sorus (Fig. 
210, C). Observe how this is attached to the veins of the pinnule. 
In such ferns as the common brake (Pteris) and the maidenhair 
(Adiantum) there is no separate indusium, but the sporangia are 
covered by the incurved edges of the fronds. 

(c) The coiled spore-cases or sporangia, lying partly covered by 
the indusium. How do these sporangia discharge their spores ? 

Make a drawing, or several drawings, to bring out all these points. 

Examine some of the sporangia, dry, with a power of about fifty 
or seventy-five diameters, and sketch. Scrape off a few sporangia, 
thus disengaging some spores, mount the latter in water, examine 
with a power of about 200 diameters, and draw. 

352. Life History of the Fern. — When a fern-spore is sown on 
damp earth it gradually develops into a minute, flattish object, 
called a prothallium (Fig. 211). It is a rather tedious process to 
grow prothallia from spores, and the easiest way to get them for 
study is to look for them on the earth or on the damp outer sm'face 
of the flower-pots in which ferns are growing in a greenhouse. All 
stages of germination may readily be found in such localities. 

Any prothallia thus obtained for study may be freed from par- 
ticles of earth by being washed, while held in very small forceps, in 
a gentle stream of water from a wash-bottle. The student should 
then mount the prothallium, bottom up, in water in a shallow cell, 



288 



FOUNDATIONS OF BOTANY 




Fig. 210. — Spore-Plant of a Fern {Aspidium FUix-mas). 
^►part of rootstock and fronds, not quite one-sixtli natural size ; fr, young fronds 
unrolling ; B, under side of a pinnule, showing sori, s ; C, section througli a 
sorus at right angles to surface of leaf, showing indusium, i, and sporangia, s ; 
D, a sporangium discharging spores. {B is not far from natural size. C and 
D are considerably magnified.) 



TYPES OF CRYPTOGAMS; PTERIDOPHYTES 



289 



cover v/ith a large cover-glass, and examine with the lowest power 
of the microscope. Note : 

(a) The abundant root-hairs, springing from the lower surface 
of the prothallium. 

(&) The variable thickness of the prothallium, near the edge, 
consisting of only one layer of cells. 

(c) (In some mature specimens) the young fern growing from 
the prothallium, as shown in Fig. 211, 5. 

The student can hardly make out for himself, without much 
expenditure of time, the structure of the antheridia and the arcTie- 
gonia (Fig. 211, A), 
by the cooperation 
of which fertilization 
takes place on much 
the same plan as that 
already described in 
the case of mosses. 
The fertilized egg- 
cell of the archego- 
nium gives rise to 
the young fern, the 
sporophyte which 
grows at first at the 
expense of the parent 
prothallium but soon 
develops roots of its 
own and leads an in- 
dependent existence. 
353. Nutrition.— 
The mature fern 
makes its living, as flowering plants do, by absorption of nutritive 
matter from .the soil and from the air, and its abundant chlorophyll 
makes it easy for the plant to decompose the supplies of carbon 
dioxide which it takes in through its stomata. 




Fig. 211. — Two Prothallia of a Fern (Aspidium). 
A, under surface of a young prothallium ; ar, arche- 
gonia ; an, antheridia ; r, rhizoids ; B, an older pro- 
thallium with a young fern-plant growing from it ; 
I, leaf of young fern, (Both x about 8.) 



290 FOUNDATIONS OF BOTANY 



FERN'S 

354. Structure, Form, and Habits of Ferns. — The struc- 
ture of ferns is much more complex than that of any of 
the groups of cryptogamous plants discussed in the earlier 
portions of the present chapter. They are possessed of 
well-defined fibro-vascular bundles, they form a variety of 
parenchymatous cells, the leaves have a distinct epidermis 
and are provided with stomata. 

Great differences in size, form, and habit of growth are 
found among the various genera of ferns. The tree ferns 
of South America and of many of the islands of the Pacific 
Ocean sometimes rise to a height of forty feet, while the 
most minute species of temperate and colder climates are not 
as large as the largest mosses. Some species climb freely, 
but most kinds are non-climbing plants of moderate size, 
with well-developed rootstocks, which are often, as in the 
case of the bracken-fern, or brake,^ and in Osmunda, very 
large in proportion to the parts of the plant visible above 
ground. 

355. Economic Value of Ferns. — Ferns of living species 
have little economic value, but are of great interest, even 
to non-botanical people, from the beauty of their foliage. 

During that vast portion of early time known to geolo- 
gists as the Carboniferous Age, the earth's surface in many 
parts must have been clothed with a growth of ferns more 
dense than is now anywhere found. These ferns, with 
other flowerless herbs and tree-like plants, produced the 
vegetable matter out of which all the principal coal beds 
of the earth have been formed. 

1 Pteris aquilina. 



TYPES OE CRYPTOGAMS; PTERIDOPHYTES 291 

356. Reproduction in Ferns. — The reproduction of ferns 
is a more interesting illustration of alternation of gen- 
erations than is afforded by mosses. The sexual plant, 
gametophyte^ is the minute prothallium, and the non- 
sexual plant, sporophyte^ which we commonly call the 
fern, is merely an outgrowth from the fertilized egg-cell, 
and physiologically no more important than the sporophyte 
of a moss, except that it supplies its own food instead of 
living parasitically. Like this sporophyte, the fern is an 
organism for the production of vegetative spores, from 
which new plants endowed with reproductive apparatus 
may grow. 

THE STUDY OF A CLUB-MOSS (LYCOPODIUM) 

357. Occurrence. — Several species of Lycopodium are common in 
rich woods in the northern and mountainous portions of the eastern 
United States. Any species may be studied. 

358. Examination. — Note whether the plant is chiefly erect or 
prostrate and vine-like. Describe the mode of branching. Are the 
leaves arranged flat-wise or equally on all sides of the stem ? Describe 
the leaves briefly. Are they all of one kind or do some portions of 
the plant evidently have smaller leaves ? 

Select fruiting specimens and determine the position of the spo- 
rangia. Is the leaf, near whose base each sporangium is situated, like 
the ordinary foliage leaves of the plant ? Are the fruiting portions 
of the plant similar in general aspect or different from the rest of 
the plant and raised above it on stalks? Examine the spores. Are 
they all of one kind ? 

If Selaginella is used in place of Lycopodium or for comparison, 
two kinds of sporangia are to be sought, differing chiefly in shape. 
Describe each briefly. Compare the number of spores in each. The 
larger spores (macrospores) germinate and at length produce pro- 
thallia bearing archegonia, while the smaller produce prothallia 
bearing antheridia. The archegonia, after fertilization, develop each 



292 



FOUNDATIONS OF BOTANY 



an embryo. This grows, remaining for a time attached to the 
macrospore, and at length forms a new spore-plant.* 

THE STUDY OF A SCOURING-RUSH (EQUISETUM) 

359. Occurrence. — The common horse-tail, Equisetum arvense, is 
widely distributed in the United States, east, west, north, and south. 
It is very often found on sand hills and along railroad embankments. 




Fig. 212. — Plant of Lycopodium {L. annotinum). 



The fruiting stems appear very early in the spring and are of short 
duration. The sterile vegetative growth follows, becoming well 
grown in June. 

360. Examination of Rootstocks and Roots. — Examine the under- 
ground portions of the plant with reference to general size, position, 
color, shape, and position of notches. After studying the stems 



TYPES OF CRYPTOGAMS; PTERIDOPHYTES 



293 



above ground insert here any evident points of comparison. Do you 
find any special forms of stem development suited to a special pur- 
pose ? Are there any organs in the nature of leaves ? 




Fig. 213. — A Scouring-Rush {Equisetum sylvaticwn). At the right is a 
colorless fertile stem, in the middle a green sterile one, and at the 
left a green fertile one. 



294 roTJNDATiONS or botany 

361. sterile Stems. — Examine the stems above ground with 
reference to their color and mode and degree of branching. What 
is the character of the leaves ? Do the stems in any sense serve as 
leaves? Observe the nodes composing the stem and note the posi- 
tion of the leaves on the stems. Do they appear to be placed several 
at the same level (whorled) ? 

Examine with a magnifying glass the surface of the stem and 
note the number of ridges and grooves. Compare the number and 
position of the leaves with reference to these. 

362. Mineral Matter in Stem. — Treat small pieces of the stem 
with strong nitric acid to remove all vegetable substance and note 
the mineral substance remaining. Treat in a similar way thin cross- 
sections and examine under the microscope. The substance is 
silica. It gives the plant its gritty feeling and its name and use as 
" scouring-rush." Of what use is it to the plant? Use of the same 
substance in outer rind of corn stem, bamboo stem, and straw of 
grains ? 

363. Microscopic Examination. — Make thin cross-sections of the 
stem and examine under the lowest power of the microscope. Make 
a diagrammatic sketch to indicate the central cavity, the number 
and position of the fibro-vascular bundles, the cavity or canal in 
each, the ring of tissue surrounding the ring of bundles, and the 
larger cavities or canals outside of this. Where is the chlorophyll 
located? Can stomata be found, and if so, what is their location 
and arrangement ? 

364. Fertile Stems. — Describe the fruiting stem with reference to 
general aspect, size, color, number, and length of internodes, position 
of spore-bearing portion, color of spores in mass, l^ote the shield- 
shaped bodies (transformed leaves or sporophylls) composing the 
cone-like "flower" and see whether any joints can be detected where 
they are attached. Examine the inner surface of the shields for 
sporangia and spores. Examine the sporangia under a low power 
of the microscope. Examine some spores under a higher power. 
Note the two bands, elaters, on each spore, crossing each other and 
attached only at the point of crossing, forming four loose appendages. 
Watch these while some one moistens them by gently breathing 
upon them as they lie uncovered on the slide under the microscope 



TYPES OF CRYPTOGAMS; PTERIDOPHYTES 



295 



and note the effect. Also note the effect of drying. How does this 
affect the spores ? Use of the bands ? 

365. Germination of Spores. — The spores germinate while fresh 
and form prothallia corresponding to those of ferns, but generally 
dioecious. The prothallium which bears the antheridia remains 
comparatively small, and the antheridia are somewhat sunken. The 
others grow much larger and branch profusely. 
The terminal portion becomes erect and ruffled. 
Near this part the archegonia are formed, quite 
similar to those of ferns. The embryo plant 
developing from the germ-cell has its first leaves 
in a whorl. This at length grows into a spore- 
plant like that shown in Fig. 213. 

About twenty-five species of Equisetum are 
known. Several may be looked for in any 
locality and may well be compared with the one 
described above, in regard to form, mode of 
branching, and mode of fruiting. 

366. Fern-Plants (Pteridophytes). — 
The Pteridophytes (literally fern-plants) 
include in their general category not only 
ferns as commonly recognized, but several 
other small groups which are very inter- 
esting on account of their diversity. All 
cryptogams higher than mosses belong in 
this group. In moss plants the individ- 
uals growing from spores and bearing 
antheridia and archegonia, the gameto- 
phytes, are full-grown leafy plants, and 
the spore-bearing plant, or sporophyte, is 
merely a stalk bearing a sporangium. In 
all the fern-plants the reverse is true. 
The individuals growing from spores and 
bearing antheridia and archegonia are of 



t 



Fig. 214.— Part of a 
Lobe of the Matvu'e 
Female Prothal- 
lium of Equisetum. 
(X about 50.) 

a, mouth of a ferti- 
lized archegonium. 



296 FOUNDATIONS OF BOTANY 

minor vegetative development {prothallia)^ while the spore- 
bearing plant is a leafy plant, even a tree in some ferns. 

The ferns in the strictest sense have sporangia derived 
from the epidermis (transformed hairs), while a few plants 
closely resembling them in general aspect {Botrychium^ etc.) 
have sporangia formed in the tissue of the leaf. 

In the next subdivision, the water-ferns (Fig. 215), there 
is little resemblance to the common ferns. The sporangia 
are in special receptacles at the basal portion of the plant. 
The spores are of two kinds, dioecious^ one on germination, 
producing antheridia, the other archegonia. This group 
includes two rooting forms, Marsilea (with leaves resem- 
bling a four-leaved clover) and Pilularia^ bearing simple 
linear leaves, and two floating forms, Salvinia (Fig. 215) 
and Azolla, 

The remaining groups of fern-plants are the horse-tails 
and the club-mosses. The horse-tails have only one kind 
of spore and are peculiar chiefly in their vegetative aspect 
(Fig. 213), while the spore-bearing leaves, or sporophylls, 
are arranged in the form of a cone, as already shown. 

The club-mosses include some plants which, as their 
name implies, have a superficial resemblance to a large 
moss, with the addition of a club-shaped stalked fruiting 
spike. These are the so-called " ground pines " and the 
running ground " evergreens " used for Christmas festoons 
in New England. Technically the group is distinguished 
by the possession of firm-walled sporangia formed singly 
near the bases of the leaves. The ordinary club-mosses 
already referred to have but one kind of spore, while 
plants called Selaginella and Isoetes have two kinds of 
spores, in this respect resembling Marsilea. In many 



TYPES OF CRYPTOGAMS; PTERIDOPHYTES 297 

species of Selaginella the leaves are arranged flat-wise on 
the stem, so that considered physiologically the branch- 
ing stem and its leaves together serve as a foliage leaf. 
In one of the commonest American forms, however, the 
stem is more nearly erect, and the leaves are all alike and 
four-ranked. 

Isoetes (quill-wort) grows attached to the soil in shallow 
water at the bottoms of ponds. It has the aspect of short 
grass growing in bunches. The large sporangia are at the 
broad bases of the leaves. 

367. High Organization of Pteridophytes. — The student 
may have noticed that in the scouring-rush and the club- 
moss studied there are groups of leaves greatly modified 
for the purpose of bearing the sporangia. These groups 
are more nearly equivalent to flowers than anything found 
in the lower spore-plants, and the fern-plants which show 
such structures deserve to be ranked just below seed-plants 
in any natural system of classification. 

The variety of tissues which occur in pteridophytes is 
frequently nearly as great as is found in ordinary seed- 
plants, and the fibro-vascular system is even better devel- 
oped in many ferns than in some seed-plants. 

Starch-making is carried on by aid of abundant chloro- 
phyll bodies contained in parenchyma-cells to which car- 
bonic acid gas is admitted by stomata. In many cases 
large amounts of reserve food are stored in extensive root- 
stocks, so that the spring growth of leaves and stems is 
extremely rapid. 



CHAPTER XXIII 
THE EVOLUTIONARY HISTORY OF PLANTS 

368. The Earliest Plant Life. —What sort of plants first 
appeared on the earth has never been positively ascertained. 
The oldest known rocks contain carbon (in the form of 
black lead or graphite) which may represent the remnants 
of plants charred at so high a temperature and under so 
great pressure as to destroy all traces of plant structure. 
Some objects supposed by many to be the remains of large 
algse have been found in rocks that date back to a very 
early period in the life history of the earth, before there 
were any backboned animals, unless possibly some fishes. 
Judging from the way in which the various groups of 
plants have made their appearance from the time when 
we can begin clearly to trace their introduction upon the 
earth, it is probable that some of the simplest and lowest 
forms of thallophytes were the first to appear. Decaying 
animal or vegetable matter must have been less abundant 
than is now the case, so that a plant that could make 
part or all of its food from raw materials would have had 
a better chance than a saprophyte that could not. Water- 
plants are usually simpler than land-plants, so it is highly 
probable that some kind of one-celled aquatic alga was 
the first plant. 

369. Fossil Plants. — Fossils are the remains or traces 
of animals or plants preserved in the earth by natural 
processes. Fossil plants, or parts of plants, are very 

298 



THE EVOLUTIONARY HISTORY OE PLANTS 299 

common ; the impressions of fern-leaves in bituminous coal 
and pieces of wood turned into a flint-like substance are 
two of the best known examples. 

The only way in which we can get knowledge about 
the animals and plants that inhabited the earth's surface 
before men did is by studying such rocks as contain the 
remains of living things. In this way a great deal of 
information has been gained about early forms of animal 
life and a less amount about early plant life, — less because 
as a general thing plants have no parts that would be 
as likely to be preserved in the rocks as are the bones 
and teeth of the higher animals and the shells of many 
lower ones. 

370. The Law of Biogenesis. — An extremely important 
principle established by the study of the development of 
animals and plants from the egg or the seed, respectively, 
to maturity is this : The development of every individual is 
a brief repetition of the development of its tribe. The prin- 
ciple just stated is known as the law of biogenesis. As 
eggs develop during the process of incubation, the young 
animals within for a considerable time remain much alike, 
and it is only at a comparatively late stage that the wing 
of the bird shows any decided difterence from the fore-leg 
of the alligator or the turtle. Zoologists in general are 
agreed that this likeness in the early stages of the life 
history of such different animals proves beyond reasonable 
doubt that they all have a common origin, that is, are 
descended from the same kind of ancestral animal. 

Among plants the liverworts and ferns supply an excel- 
lent illustration of the same piinciple. In both of the groups 
the fertilized egg-cells, as the student may have learned 



300 FOUNDATIONS OE BOTANY 

by his own observations, are much alike. As the egg-cell 
grows and develops, the sporophyte of a liverwort, which 
proceeds from the egg-cell, is extraordinarily unlike the 
" fern" or asexual generation (gametophyte) among Filices. 
Now this progressive unlike ness between liverworts and 
ferns, as they develop from the fertilized egg-cell, points to 
the conclusion that both groups of plants have a common 
origin or that the more highly organized ferns are direct 
descendants of the less highly organized liverworts. 

371. Plants form an Ascending Series. — All modern 
systems of classification group plants in such a way as to 
show a succession of steps, often irregular and broken, 
seldom leading straight upward, from very simple forms 
to highly complex ones. The humblest thallophytes are 
merely single cells, usually of microscopic size. Class 
after class shows an increase in complexity of structure 
and of function until the most perfectly organized plants 
are met with among the dicotyledonous angiosperms. 
During the latter half of the present century it first 
became evident to botanists that among plants deep-seated 
resemblances imply actual relationship^ the plants which 
resemble each other most are most closely aJdn by descent, 
and (if it ivere not for the fact that countless forms of plant 
life have wholly disappeared) the whole vegetable kingdom 
might have the relationships of its members worked out by a 
sufficiently careful study of the life histories of individual 
plants and the likeness and differences of the several groups 
which make up the system of classification.^ 

1 See Campbell's Evolution of Plants and Warming's Systematic Botamj, 
Preface and throughout the work. In the little flora of the present book, the 
families are arranged in the order which, according to the best recent German 
authorities, most nearly represents their relationships. 



THE EVOLUTIONARY HISTORY OF PLANTS 301 

372. Development of the Plant from the Spore in Green 
Algae, Liverworts, and Mosses. — The course which the 
forms of plant life have followed in their successive ap- 
pearance on the earth may be traced by the application 
of the law above named. Such algse as the pond-scums 
produce spores which give rise directly to plants like the 
parent. 

In many liverworts the spore by its germination produces 
a thallus which at length bears antheridia and archegonia. 
The fertilized archegonium develops into a sporophyte 
which remains attached to the thallus, although it is really 
a new organism. Liverworts, then, show an alternation of 
generations, one a sexual thallus, the gametophyte, the 
next a much smaller, non-sexual sporophyte, and so on. 

A moss-spore in germination produces a thread-like pro- 
tonema which appears very similar to green algee of the 
pond-scum sort. This at length develops into a plant with 
stem and leaves, the sexual generation of the moss. The 
fertilized archegonium matures into a sporophyte which is 
the alternate, non-sexual generation. This is attached to 
the moss-plant, or gametophyte, but is an important new 
organism. In the moss, as in the liverwort, the sexual 
generation is the larger and the more complex ; the non- 
sexual generation being smaller and wholly dependent for 
its food supply on the other generation, to which it is 
attached. 

373. Development of the Plant from the Spore in Pterido- 
phytes. — In the pteridophytes there is an alternation of 
generations, but here the proportions are reversed, the 
prothallium, or sexual generation, or gametophyte, being 
short-lived and small (sometimes microscopic), and the 



302 



FOUNDATIONS OF BOTANY 



non-sexual generation, the sporophyte, often being of large 

size. The ferns (non-sexual generation), for instance, are 
perennial plants, some of them tree- 
like. 

Some pteridophytes, as the Salvinia, 
a small floating aquatic plant, some- 
times known as a water-fern (Fig. 
215), produce two kinds of spores, 
the large ones known as macrospores^ 
and the small ones known as micro- 
spores (Fig. 216). Both kinds pro- 
duce microscopic prothallia, those of 
the former bearing only archegonia, 
those of the latter only antheridia. 
From the prothallia of the macro- 
spores a plant (non-sexual generation) 
of considerable complexity of struc- 
ture is formed. 
374. Parts of the Flower which correspond to Spores. — 

In seed-plants the spore-formation of cryptogams is repre- 
sented, though in a way not 

at all evident without careful 

explanation. The pistil is the 

macrospore-producing leaf or mac- 

rosporophyll, and the stamen is 

the microspore-producing leaf or 

microsporophyll. Pines and other 

gymnosperms produce a large cell 

(the embryo sac) in the ovule 

(Fig. 217), which corresponds to the macrospore, and a 

pollen grain which represents the microspore. In its 




Fig. 215.— a Water-Fern 
(Salvinia). 




Fig. 21 6.— Two Indusiaof Salvinia. 

mi, microspores ; ma, macro- 
spores. 



THE EVOLUTIONARY HISTORY OE PLANTS 



303 



development the macrospore produces an endosperm which 
is really a small cellular prothallium, concealed in the ovule. 
The microspore contains vestiges of a minute prothallium. 

In the angiosperms the macrospore and its prothallium 
are still less developed, and the 
microspore, or pollen grain, has 
lost all traces of a prothallium 
and is merely an antheridium 
which contains two generative 
cells.^ These are most easily 
seen in the pollen grain, but 
sometimes they are plainly visi- 
ble in the pollen tube (Fig. 164). 
Phanerogams are distinguished 
from all other plants by their 
power of producing seeds, or 
enclosed macrosporangia, with 
embryos. 

375. The Law of Biogenesis 
and the Relationships of the Great 
Groups of Plants. — On summing 
up Sects. 372-374 it is evident 
that the sexual generation in 
general occupies a less and less 
important share in the life of the 
plant as one goes higher in the scale of plant life.^ In the 
case of the rockweed, for instance, the sexual generation 
is the plant. Among mosses and liverworts the sexual 

1 Sometimes only one generative cell escapes from the pollen grain into the 
pollen tube, and there it divides into two cells. 

2 A good many plants of low organization, however, are not known to pass 
through any sexual stage. 




Fig. 217. — Longitudinal Section 
through Fertilized Ovule of a 
Spruce. 

p, pollen grains ; t, pollen tubes ; 
«, neck of the archegonium ; 
a, body of archegonium with 
nucleus ; e, embryo sac filled 
with endosperm. 



304 FOUNDATIONS OF BOTANY 

generation is still very prominent in the life of the plant. 
Ordinary ferns show us the sexual generation existing only 
as a tiny independent organism, living on food materials 
which it derives from the earth and air. In the Salvinia 
it is reduced to microscopic size and is wholly dependent 
on the parent-plant for support. Among seed-plants the 
sexual generation is so short-lived, so microscopic, and so 
largely enclosed by the tissues of the flower that it is com- 
paratively hard to demonstrate that it exists. 

The fact that the life history of so many of the classes 
of plants embraces a sexual stage, in which an egg-cell is 
fertilized by some sort of specialized cell produced wholly 
for use in fertilization, tends strongly to show the com- 
mon origin of the plants of all such classes. We have 
reason to believe, from the evidence afforded by fossils, 
that plants which have only a sexual generation are 
among the oldest on the earth. It is therefore likely that 
those which spend the least portion of their entire life in 
the sexual condition were among the latest of plants to 
appear. Then, too, those which have the least developed 
sexual generation are among the latest of plants. Judged 
by these tests the angiosperms must be the most recently 
developed of all plants. 

If one were to attempt to arrange all the classes of 
existing plants in a sort of branching series to show the 
way in which the higher plants have actually descended 
from the lower, he would probably put some one of the 
green algge at the bottom and the angiosperms at the top 
of the series. 

376. The Oldest Angiosperms. — It is impossible to give 
any of the reasons for the statements of this section 



THE EVOLUTIONARY HISTORY OF PLANTS 305 

without making an unduly long chapter. Briefly, it may 
be stated that the monocotyledons are the simplest and 
probably the oldest angiosperms; the dicotyledons are 
higher in organization and came later. The descent and 
various relationships of the families of dicotyledons can 
be discovered by the study of the flower, fruit, and seed 
better than by the examination of the vegetative organs. 

The entire pedigree of the several families cannot be 
represented by arranging the names of the families in a 
straight line. It is, however, in a general way, as indi- 
cated by the succession of families in the Flora which 
accompanies this book, the Willow Family being perhaps 
the oldest (of the more familiar ones) and the Composite 
Family the youngest. 



INDEX 



Starred page-numbers indicate where cuts occur. 



Parts I and II 



Absorption of carbon dioxide, 166- 
170. 

Acacia, leaf of, *145. 

Accessory buds, 122, *123. 

Accessory fruits, *226. 

Acuminate, *131. 

Acute, *131. 

Adaptations to conditions of exist- 
ence, 394. 

Adherent, 204. 

Adnate, 204. 

Adventitious buds, 128. 

Adventitious roots, 36. 

Aerial roots, 36, *37, *38, *39. 

Agaricus, study of, 264-266*. 

Age of trees, 71. 

Aggregate fruits, 225, *226. 

Ailanthus tvrig, *121. 

Air, relation to germination, 10- 
12. 

Air chamber, *151, *163, *154. 

Air-passages in Hippurisstem,*173. 

Akene, *222. 

Albuminous substances, 22. 

AlgsB, 232, 241-257*. 

Algae, classification of, *257. 

Algae, study of, 241-257* 



Alternate, *65, 66. ] 

Alternate leaves, *140. ' 
Alternation of generations, 278. 

Althaea leaf, *152. \ 

Anatomy of plants (see under root, i 

stem, leaf, flower, fruit, structure 

of). 

Angiosperms, 233. * i 
Angiosperms, oldest, 304, 305. 

Animal food, need of, 344. ! 
Animals, defenses against, 345- 

352*. : 

Annual growth, indefinite, 69. \ 

Annual ring, *100, *101. j 

Annuals, 71. i 

Anther, 201, 202, *203. I 

Anther, modes of opening, *211. \ 

Antheridia, *284, 285. j 

Antherozoids, 247, 248, *251, 254. j 

*279, *284. I 

Antipodal cells, *215. i 

Ant-plants, 346, *347. | 

Ants plant seeds, *386. j 

Apetalous, *198. \ 

Apothecia, 271. > 

Apple leaf, stipules of, *135. ! 
Aquatic roots, 37. 



397 



398 



FOUNDATIONS OF BOTANY 



Arch of hypocotyl, 25-27. 
Archegonia, *284, 285, *295. 
Arctic willow, *328. 
Aristolochia stem, bundle of, *88. 
Aristolochia stem, cross-section of, 

*87, 88. 
Arrangement of leaves, *140, *141. 
Arrow-shaped, *132. 
Asci, 263, 270, 273. 
Ascomycetes, 232. 
Asexual generation, 278. 
Ash tree, naturally grafted, *99. 
Asparagus, 79, *80. 
Aspidium, *288. 
Asplenium, study of, 286-289*. 
Assimilation, 171, 172. 
Autumn leaves, coloration of, 176. 
Axillary bud, *122. 
Axillary flowers, *186. 

Bacillariales, 232. 

Bacilli, *237. 

Bacteria, 232, *237. 

Bacteria, manufacture of nitric acid 

by, 340. 
Bacteria, study of, 238, 239. 
Barbed hairs, *351. 
Barberry, spiny leaves of, *348. 
Bark, 86, *91, 104. 
Basidia, *266. 
Basidiomycetes, 232. 
Bast, *87, *91, *92. 
Bast-bundle, *92. 
Bean-pod, study of, 219. 
Bean seed, 7, 8. 
Beech twig, 64. 

Beech-wood, cross-section of, *101. 
Bees, 355, *356, *360. 
Beet leaf, *151. 
Beggar's ticks, *384. 
Begonia leaf, osmose in, 51. 



Bell-shaped, *202. 

Belt's bodies, *347. 

Berry, *225. 

Berry, study of, 217. 

Biennial, 47, 71. 

Biogenesis, law of, 299, 300. 

Birch, branching of, *71. 

Bird-pollinated flowers, 362. 

Birds plant seeds, 385, *386. 

Black mould, study of, 257, 258, 

259. 
Bladder-wrack, *250. 
Botanical geography, 324-335. 
Botanical geography of United 

States, 333-335. 
Botany, definition of, 1. 
Box-elder, buds of, *123. 
Box-elder, radial and cross-sections 

of stem of, *89. 
Bract, *186, 187. 
Branches formed from adventitious 

buds, 128. 
Branching, alternate, *65, 66. 
Branching and leaf-arrangement, 

64, 65. 
Branching, opposite, *65. 
Branch-spine, *69. 
Brazil nut, food stored in, 23, 24. 
Breathing-pore, *153. 
Bryophytes, 232, 277, 278. 
Buckeye, bud of, *120. 
Bud, horse-chestnut, 119, 120. 
Bud-scales, 121. 
Buds, 118-129. 
Buds, adventitious, 128. 
Buds, dormant, 127, 128. 
Buds, naked, 121. 
Buds, position of, 121, *122, *123, 

*124. 
Buds, structure of, 119, *125. 



INDEX 



399 



Bulb, hyacinth, *79. 

Bulb, onion, 77. 

Bulblets, 375, 376. 

Bulrush, cross-section of stem of, 

*84. 
Burs, 381, 382, *383. 
Buttercup, leaf of, *135. 
Buttercup, study of flower of, 195. 

196. 
Butternut, buds of, *124. 

Cabbage, a bud, 123. 

Cactus, *80, *315. 

Cactus flower, transitions in, *208. 

Caladium, 76, *77. 

Calyx, *197. 

Cambium, *87, *88, *89, 95-100. 

Cambium-ring, 96, *97. 

Canna, parallel veining in, 136. 

Capsule, 223. 

Carbon dioxide, absorption of, 166- 

168. 
Carbon dioxide, disposition of, 168, 

169. 
Carnivorous plants, 342-344*. 
Carpel, 198. 

Castor bean, germination of, *7. 
Castor-oil plant, early history of 

stem, *95. 
Castor-oil plant, fibro-vascular 

bundle of, *95. 
Catharinea, *282. 
Catkin, *187. 
Celandine, leaf of, *134. 
Cell, 20, 21. 
Cell-contents, *19, *155, 180, *183, 

*184. 
Cell-contents, continuity of, 146. 
Cell-division, *183, *242, 245. 
Cell-multiplication in pond-scum, 

*242. 



Cell-sap, *183. 

Cell, simplest form of, 178, *179, 

180. 
Cell-wall, 178. 
Cells, isolated wood-, *91. 
Cellulose, a compound of carbon, 

hydrogen, and oxygen ; the chief 

constituent of ordinary cell-walls, 

156, 171, 268. 
Central cylinder, *42. 
Central placenta, *205. 
Chara, *248, *249. 
Characeae, 249, 250. 
Chemical changes in leaves before 

falling, 175, 176. 
Cherry, buds in axils of leaves, 

*122. 
Cherry twig, *63, *125. 
Chestnut fruit, *222. 
Chlorophyceae, 232. 
Chlorophyll, 168, 169, 176. 
Chlorophyll bodies, *154, *155. 
Cilium, 180. 
Circulation of protoplasm, *184, 

185. 
Cladophyll, 79, *81. 
Class, 231. 

Classification, 228-234. 
Cleistogamous flowers, 369, *370. 
Clerodendron, *363. 
Climbing plants, 73-75*. 
Climbing shrubs, stem-structure, 

99, 100. 
CHmbing stems, *73, *74, *75. 
Clinostat, *58, 59. 
Clover leaf, *144. 
Club-moss, study of, 291, *292. 
Cluster-cup, 259, *261. 
Coherent, 200. 
Cohesion, 204, *205. 
Collenchyma, *95. 



400 



FOUNDATIONS OF BOTANY 



Colocasia, *77. 

Coloration of autumn leaves, 176. 
Colors of flowers, 357, 358. 
Common receptacle, *189. 
Compass-plant, nearly vertical 

leaves of, *147. 
Composite head, 188, *189, 190. 
Compound cyme, *191. 
Compound leaves, *137, *138, 139. 
Compound pistil, 202. 
Compound umbel, *189. 
Conceptacles, 250, *252. 
Condensed stems, 78. 
Conifers, wood of, *93, *94. 
Coniferous wood, structure of, 92, 

*93, *94. 
Conjugate, 232. 
Conjugating cell, *243, *259. 
Conjugation, *243. 
Consolidated, 204. 
Continuity of protoplasm, 146. 
Contractile vacuole, 180. 
Contractility, 182. 
Cork, 90, *100, 104, 115. 
Corm, a bulb-like, fleshy stem, or 

base of stem, " a solid bulb." 
Corn, aerial roots of, *38. 
Corn, cross-section of stem of, *83. 
Corn, germination of, 8. 
Corn, grain of, *16. 
Corn, root- tip, section, *42. 
Corn-stem, structure of, *83, 84. 
Corolla, *197. 
Corymb, *186, 187. 
Cotyledon, 7. 
Cotyledon, disposition made of, 28, 

29. 
Cotyledons, thickened, use of, 29. 
Crenate, 132. 
Cross-pollination, 353. 
Crow-berry, rolled-up leaf of, *317. 



Cryptogams, 231. 

Cryptogams, classes of, 232, 233. 

Cuspidate, *131. 

Cuticle, unequal development of, by 

epidermis-cells, 156, *157. 
Cutin, 156. 
Cutting leaves, *351. 
Cyme, *191. 
Cypress, 71. 

Dahlia, thickened roots of, *41. 
Daily movements of leaves, *144, 

*145, *146. 
Dandelion, *72. 
Darwin, Charles, 353. 
Date-palms, *85. 
Datura, stigma of, *213. 
Deciduous, 175. 

Defenses against animals, 345-352.* 
Definite annual growth, 69. 
Dehiscent fruits, 222, *223. 
Deliquescent trunk, 66, *67. 
Dentate, 132. 

Descent of water, 109, *110. 
Desert, Sahara, *325. 
Desmids, *243. 

Destruction of plants, 391, 392. 
Determinate inflorescence, 191. 
Deutzia leaves, *142, *143. 
Diadelphous, 202. 
Diagrams, floral, 204, *205, *296. 
Diatoms, study of, *240, 241. 
Dichogamy, *363, *364. 
Dicotyledonous plants, 34, 233. 
Dicotyledonous stem, annual, gross 

structure of, 86, *87. 
Dicotyledonous stem, cross-section 

of, *87, *89, *91, *96, *100. 
Dicotyledonous stem, mechanical 

importance of distribution of 

material in, 89, 90. 



INDEX 



401 



Dicotyledonous stem, minute struc- 
ture of, 86-98*. 

Dicotyledonous stem, rise of water 
in, 107, 108, *109. 

Dimorphous flowers, *366, 367. 

Dioecious, 200. 

Discharge of pollen, *211. 

Disk-flowers, 188, *189. 

Dispersal of seeds, 376-386*. 

Dispersal of seed-plants, 373-376. 

Distinct, 201. 

Distribution of material in mono- 
cotyledonous stems, *84, 85. 

Dock fruit, study of, 219, 220. 

Dodder, 39, *40, 41. 

Dormant buds, 127, 128. 

Double flowers, 209. 

Drip-leaves, *314. 

Drosera, *341, *342, 843. 

Drought, endurance of, 162, 163. 

Drought-plants, 313-317*. 

Dry fruits, 224. 

Duckweed, 314. 

Duct, *92. 

Earliest plants, 298. 
Ecology, 2, 307. 
Egg, osmosis in, 50, *51. 
Egg-cell, *249, *251, 280, *284, 285. 
Elaters, 294. 
, Elliptical, *131. 
Elm, *67. 
Elm bud, *125. 
Elm fruit, *223. 
Elm leaf, 130, 133. 
Elm, twig of, *125. . 
Emarginate, *131. 
Embryo, 6, 17. 
Embryo sac, *215. 
Endosperm, *15, *16, 17, 19. 
Energy, source of, in plants, 173. 



Enslaved plants, 338, *339. 
Epidermis, uses of, 156, *157. 
Epidermis of root, *42, *44. 
Epigynous, 204, *205. 
Epipetalous, 204, *205. 
Epiphytes, 322, *323. 
Equisetales, 232. 
Equisetum, study of, 292-295*. 
Essential organs, *197. 
Euphorbia splendens, *350. 
Evergreen, 175. 
Evolutionary history of plants, 

298-305. 
Excretion of water, 172, 173. 
Excurrent trunk, *66. 
Existence, struggle for, 387-393. 
Exogenous, 96, 
Explosive fruits, 377. 

Fall of horse-chestnut leaf, *137. 
Fall of the leaf, 175, 176. 
Family, 230. 

Family, subdivisions of, 231. 
Fascicled roots, *41. 
Fermentation, 269. 
Fern, study of, 286-289*. 
Fern-plants, 295-297. 
Ferns, 290, 291. 
Fertilization, *214, *215, 216. 
Fibrous roots, *41. 
Fibro-vascular bundles, *83. 
Ficus elastica, leaf of, *154. 
Ficus religiosa, drip-leaf of, *314. 
Fig, transpiration in, 160, *161, 

162. 
Filament, 201, 202, *203. 
Filicales, 232. 
Fir wood, *93. 
Fission, *242. 
Fission-plants, 232. 
Fittest, survival of, 394, 395. 



402 



rOUNDATIONS OF BOTANY 



Elax, cross-section of stem of, *91. 

Fleshy fruits, 224. 

Fleshy fruits, uses of, 383-385. 

Fleshy roots, 45, 46, *47. 

Floating seeds, 381. 

Floral diagrams, 204, *205, *206. 

Floral envelopes, 198. 

Floral organs, movements of, 365, 

366. 
Floridese, 255. 

Flower, nature of, 208-211*. 
Flower, organs of, *197. 
Flower, plan of, 197-206*. 
Flower-buds, position of, 186. 
Flowerless plants, 232, 233, 235- 

297. 
Flowers, bird-pollinated, 362. 
Flowers, colors of, 357, 358. 
Flowers, ecology of, 353-372*. 
Flowers, odors of, 357. 
Flytrap, Venus, *343, 344. 
Follicle, *223. 
Food in embryo, 14. 
Food, storage of, in root, 46, *47. 
Food, storage of, in stem, 113-117. 
Food, storage outside of embryo, 

15. 
Formative tissue, 95. 
Fossil plants, 298, 299. 
Fossils, 298. 
Four-o'clock seed, 15. 
Foxglove, pinnate leaf of, *133. 
Free, 204. 

Free central placentation, *205. 
Frond, 287, *288. 
Frost, action of, 394. 
Fruit, 221-227*. 
Fruit, definition of, 221. 
Fruit-dots, *288. 
Fruits, study of, 217-220. 
Fruits, uses of, 376-386*. 



Fucus, 250-252*. 
Funaria, *284. 
Fungi, 232, 274-276. 

Gametophyte, 291. 

Gamopetalous, 200. 

Gamosepalous, 200. 

Gemmse, 279. 

Generations, alternation of, 278. 

Generative cells, in pollen tube, 

*214. 
Genus, 229. 

Geography, botanical, 324-335. 
Geography, botanical, of the United 

States, 333-335. 
Geotropism, *57, *58, 59, 68. 
Germination, 5-13. 
Germination, chemical changes 

during, 11-13. 
Germination, conditions of, 8-11. 
Gills, *264, 265. 
Gonidia, 273. 
Gourd-fruit, 224. 
Grafting, 98, *99. 
Grain, 222. 

Grape sugar, test for, 116, 117. 
Gray, Asa, 71. 
Green layer of bark, 86, *91. 
Groups, 231. 
Growing point, *42. 
Growth, measurement of, in stem, 

32. 
Growth, secondary, *96, *97, *100: 
Guard-cells, *151, *153, *154, 158, 

159. 
Gymnosperms, 233. 

Haematococcus, *244. 
Hairs, 158. 

Hairs, stinging, 349, 350, *351. 
Halberd-shaped, *132. 



INDEX 



403 



Half-parasites, 336, 

Halophytes, 311, *319, 320, *326. 

Hard bast, *87, *91, *92. 

Haustoria, 39. 

Head, *188. 

Heart-shaped, *132. 

Heartwood, 105. 

Heliotropism, 148. 

Hemlock, lateral extension of 
roots, *60. 

Hepaticse, 232, 280, 281. 

Hepaticse, study of, 278-280*. 

Herbs, 70. 

Hesperidium, *225. 

High mallow, provisions for cross- 
pollination of, *364. 

Hilum, 6. 

Honey-bee, leg of, *356. 

Honey-gland, *357. 

Honey locust, spine, *69. 

Hop, twining of, *75. 

Hormogonia, *238. 

Horse-chestnut bud, study of, 119, 
120. 

Horse-chestnut, germination, 8. 

Horse-chestnut twig, 62-64. 

Host, 39. 

Hot springs, plants in, 393. 

Hyacinth, bulb of, *79. 

Hybrid, 229. 

Hybridization, 229. 

Hydrangea, transpiration in, 159- 
161* 

Hydrogen, 168. 

Hydrophytes, 311, *312, *313, 
*314. 

Hymenium, *265. 

Hyphse, 257, *258. 

Hypocotyl, 6, 25-27. 

Hypocotyl, cross-section of, 95. 

Hypogynous, 204, *205. 



Iceland moss, 274, 

Imperfect flowers, 199. ! 

Indefinite annual growth, 69. '] 

Indehiscent fruits, 221, *222. 1 

Indeterminate inflorescence, 186. j 

Indian corn, germination of, 8. 
Indian corn, kernel of, 16. 
Indian corn, root-tip, *42, 43. 
Indian corn, structure of stem, 

*83, 84. 
Indian pipe, 169. 
India-rubber plant, leaf of, *154. 
India-rubber plant, transpiration 

of, 160-162. 
Indusium, 287, *288. 
Liflorescence, 186-191*. 
Inflorescence, determinate, 191. 
Inflorescence, diagrams of, *190. 
Inflorescence, indeterminate, 186. 
Insectivorous plants, 340-344*. 
Insect pollination, 355-369*. 
Insect pollination, study of, 367- 

369. 
Insects, pollen-carrying apparatus 

of, 355, *356. 
Insects, sense of smell of, 357. 
Insects, vision of, 358. 
Insect-traps, leaves as, *342, *343. 
Insect visits, 358-362* *365. 
Insertion of floral organs, *205. 
Intercellular spaces, *95. 
Internode, 32, 83. 
Involucre, 188, *189. 
Ipomoea Jalapa, 46. 
Ipomoea, rate of increase of, 390-, 

391. 
Iris, rootstock of, *77. 
Irish moss, 253. 
Irritability in plants, nature and 

occurrence of, 182-184. 
Ivy, aerial roots of, *39. 



404 



FOUNDATIONS OF BOTANY 



Keel, *199. 
Kidney-shaped, *131. 
Knots, *102. 

Labiate, *203. 

Lady fern, 286. 

Lanceolate, *131. 

Lateral buds, 63, 12L 

Leaf, 130-139* 

Leaf, accumulation of mineral 
matter in, 165. 

Leaf-arrangement, *140,*141, *142, 
*143. 

Leaf-bases, *132. 

Leaf-buds, 122, 123. 

Leaf, fall of, 175, 176. 

Leaf-like stems, 78, 79, *81. 

Leaf-margins, *132. 

Leaf-mosaics, 142, *143. 

Leaf-outlines, *131. 

Leaf-sections, *151, *154. 

Leaf-spine, *348. 

Leaf-stalk, 130. 

Leaf -tendril, *138. 

Leaf-tips, *131. 

Leaf-traces, 155. 

Leaves as insect-traps, *342, *343. 

Leaves, compound, *137, *138, 139. 

Leaves cutting, 350, *351. 

Leaves, divided, 143. 

Leaves, functions of, 155-174. 

Leaves, movements of, *144, *145, 
*146. 

Leaves, simple, 137. 

Leaves, structure of, 150-158* 

Legume, 223. 

Lemon, study of, 217, 218. 

Lenticels, 104. 

Leucoium, pollen tube with gener- 
ative cells, *214. 

Lianas, *73. 



Lichen, 232. 

Lichenes, 232. 

Lichens, nature of, 273, 274. 

Lichens, study of, 270-273*. 

Light, exposure to, 140-149*. 

Light, movements towards, 148, 

149. 
Lignin, 171, 172. 
Lily leaf, 150. 
Lily, pollen grains producing tubes 

on stigma, *214. 
Limb of calyx or corolla, 200. 
Lime, 165. 

Linden, fruit cluster of, *377. 
Linden fruit, *377. 
Linden wood, structure of, *100. 
Linear, *131. 
Liverworts, 277-281* 
Living parts of the stem, 104, 105. 
Lobe, 201. 
Locules, 203. 
Locust, pinnately compound leaf 

of, *138. 
Locust, thorn-stipules of, 350. 
Luffa, 86. 
Lupine, white, 8. 
Lycopodiales, 232. 
Lycopodium, study of, 291, *292. 

Macrospores, 291, *302. 

Macrosporophyll, 302. 

Magnolia, forking of, *70, *71. • 

Mahogany wood, structure of, *101. 

Maldive nut, 381. 

Mallows, pollination in, 364. 

Malt, 13. 

Maltose, 116. 

Mangrove, *319. ^ 

Maple fruit, *223. 

Maple leaf, 134. 

Marchantia, study of, 278-281*. 



IOT)EX 



405 



Marestail, air-passages of, *173. 
Mechanics of monocotyledonous 

stems, *84, 85. 
Medullary ray, 45, *101. 
Melon, palmately netted-veined 

leaf of, *133. 
Melon-cactus, 78, *80. 
Messmates, 340. 
Mesophytes, 317, 318. 
Mesquite, root-system of, 48. 
Metabolism, 165-176. 
Metabolism, digestive, 172. 
Micropyle, 6. 

Microsphaera, study of, 263, 264. 
Microspores, *302. 
Microsporophyll, 302. 
Midrib, *133. 

Mildews, powdery, 263, *264. 
Mimicry, 347, 348. 
Mineral matter accumulated in the 

leaf, 165. 
Mistletoe, 337. 
Modified leaves, 121. 
Moisture-plants, 311-313. 
Monadelphous, 202, *204. 
Monocotyledonous plants, 34, 233. 
Monocotyledonous stems, *83, *84, 

*85, 86. 
Monocotyledonous stems, growth 

of, in thickness, 85, 86. 
Monocotyledonous stems, rise of 

water in, *110. 
Monocotyledons, 233. 
Monoecious, 200. 
Monotropa, 169. 
Morning-glory, rate of increase of, 

390, 391. 
Morphology, 1, 33. 
Moss, study of, 281-285. 
Mosses, 281-285* 
Moths, *361, 362. 



Mould, black, study of, 257, 258, 

259. 
Movement of water in plants, 107, 

*108, *109, *110, 111, 112, 113. 
Movements of floral organs, *365, 

*366. 
Movements of leaves, *144, *145, 

*146. 
Movements toward light, 148. 
Mucronate, *131. 
Mulberry, *226. 
Mullein, hairs from corolla of, 

*361. 
Multiple fruits, *226. 
Multiple primary roots, 14. 
Musci, 232. 

Mushroom, study of, 264-266*. 
Mutilated seedUngs, growth of, 14. 
Mycelium, 257, *258. 
Mykorhiza, 342. 
Myrsiphyllum, 79, *81. 
Myxogasteres, 232. 
Myxothallophytes, 232, 233. 

Naked buds, 121. 

Nasturtium leaves, starch in, *170. 

Natural selection, 394, 395. 

Nectar, 356. 

Nee car-glands, 356. 

Nectar-guides, 358. 

Nectaries, 357. 

Negundo, radial and cross-sections 

of stem of, *89. 
Nemalion, study of, 253, 254, *255. 
Netted-veined, *133. 
Nettle, stinging hair of, *184. 
Nightshade, leaf of, *349. 
Nitella, study of, 247-250. 
Nitrogen, 171, 340. 
Nocturnal position, *144, *145. 
Node, 31, 32, 83. 



406 



FOUNDATIONS OF BOTANY 



Nucleus, 178. 

Nucleus of root-hair, *49. 

Nut, *222, 223. 

Nutrient substances, 168, 169, 171. 

Nutrition of plants, 165-176. 

Oak leaves, arrangement of, *140. 

Oat, root-system of, 48. 

Obovate, *131. 

Obtuse, *131. 

Odors of flowers, 357. 

Offensive-smelling plants, 352. 

Oil, 21, 22. 

Oil, essential, 24. 

Oil, extraction, 22. 

Oil, testing seeds for, 21, 22. 

Onion, bulb of, 77. 

Onion leaf, section of, *79. 

Onion, structure of, 116. 

Onion, tests for food-materials in, 

116, 117. 
Oogonia, *251. 
Oosphere, *249, *251, 280, *284, 

285. 
Oospore, 247, 249. 
Opposite, *65, *140, *141, *142. 
Orbicular, *131. 
Orchid, aerial roots of an, *37. 
Order, 230. 

Organs, essential, *197. 
Organs, vegetative, 30. 
Oscillatoria, study of, 239, 240. 
Osmosis, 50-54. 
Osmosis in an egg, 50, *51. 
Osmosis in root-hairs, 53, 54. 
Ovary, 201, 202, *203, *205. 
Ovate, *131. 
Ovoid, egg-shaped. 
Ovule, 202, *203. 
Ovule, spruce, fertilized, *303. 
Ovule, structure of, *215. 



Oxalis leaf, development of, *127. 
Oxidation, 11, 12. 
Oxygen, 11, 12, 166, 167, 168. 
Oxygen-making, 167, 168. 

Palisade-cells, *151. 

Palmate, *133. 

Pampas region, 393. 

Panicle, *189, 190. 

Panicum, *381. 

Pansy, leaf-like stipules of, *135. 

Papilionaceous corolla, *199. 

Papillae on stigma of a lily, *214. 

Paraphyses, 251, *252. 

Parasites, 39, 336-338. 

Parasitic roots, 39, *40. 

Parenchyma, 94. 

Parietal placenta, 203, *205. 

Parsnip root, study of, 45, 46. 

Pea seed, 8. 

Pea seedling, mutilated, 14. 

Pea seedling on clinostat, 58. 

Peat bogs, 327. 

Peat moss, *327. 

Pedicel, *186, 187. 

Peduncle, *186, 187. 

Peg of squash seedling, 27. 

Pepo, 224. 

Perennial, 47, 71. 

Perfect, 198. 

Perianth, *197. 

Pericarp, 224. 

Perigynous, 204, *205. 

Perithecia, 263. 

Permanganate test, 28. 

Petal, 197. 

Petiole, 130, 134. 

Phseophycese, 232. 

Phanerogams, 231, 233. 

Phanerogams, classes of, 233. 

Phosphorus, 165. 



INDEX 



407 



Phycomycetes, 232. 

Physcia, 270-273. 

Physiology, vegetable, 1. 

Pigeon-wheat moss, study of, 281- 
285. 

Pileus, *264, 265. 

Pine, seedling, *33. 

Pine wood, *94. 

Pinnae, leaflets of a pinnately com- 
pound leaf, 138. 

Pinnate, *133. 

Pinnules, *288. 

Pistil, *197, 201, 202, *203. 

Pistil, parts of, *203. 

Pitcher-plant, *340. 

Pith, *83, *87, *88, *89. 

Placenta, 203, *205. 

Plankton, 333. 

Plant colonies, 310. 

Plant formations, 310. 

Plant physiology, definition of, 1. 

Plant societies, 307-323, *312,*322. 

Plants of uneatable texture, 348. 

Plants, classes of, in relation to 
economy of water, 311. 

Plants, destruction of, by animals, 
345. 

Plants, earliest appearance of, 298. 

Plants, mimicry by, 347, 348. 

Plasmolysis, 62, 53. 

Pleurococcus, study of, 244, 245. 

Plumule, 7. 

Pod, 219, 223. 

Poisonous plants, 352. 

Poisonous seeds, 24. 

Poisons, plants containing, 352. 

Pollarded trees, 128. 

Pollen, 201, 211, *212. 

Pollen-carrying apparatus, 355, 
366. 

Pollen, discharge of, *211. 



Pollen grains, *212. 

Pollen grains, number of, per 

ovule, 216. 
Pollen, protection of, from visitors, 

360-362. 
Pollen, protection of, from rain, 

*371, 372. 
Pollen tubes, 212, 213, *214. 
Pollination, 353-355. 
Polypetalous, 201. 
Polysepalous, 201. 
Polysiphonia, 255. 
Polytrichum, 281-285. 
Pome, 224. 

Pond-scum, study of, 241-244*. 
Potash in hay, 165. 
Potato tuber, 76, *78, 114-116. 
Prickle, *349. 
Prickly leaves, *349. 
Prickly pear, *315. 
Primary root, 36. 
Primrose, pollination in flowers of, 

*366, 367. 
Procambium, *96. 
Prosenchyma, 94, 95, 
Propagation, by root, 61. 
Propagation, means of, among 

cryptogams, 373. 
Propagation of plants, 373-386*. 
Protection of plants from animals, 

345-352. 
Protection of pollen from rain, 

*371, 372. 
Proteids, 22, 23. 
Proteids, tests for, 23. 
Prothallium, 287, *289. 
Protococcus, *244. 
Protonema, 283. 
Protoplasm, 52, 178. 
Protoplasm, characteristics of, 181, 

182. 



408 



FOUNDATIONS OF BOTANY 



Protoplasm, circulation of, *184, 

185. 
Protoplasm, continuity of, 146. 
Pteridophytes, 232. 
Pteridophytes, remarks on, 286, 

295-297. 
Puccinia, study of, 259-262*. 
Pulvini, 145, *146. 

Race, 230. 
Raceme, *186. 
Raspberry, *374. 
Ray, medullary, 45. 
Ray-flowers, 188, *189. 
Receptacle, 199. 
Red clover, leaf of, *144. 
Regions of vegetation, 324. 
Regular flowers, 198. 
" Reindeer moss," 274. 
Reproduction in algse, 256. 
Reproduction in ferns, 287, *288, 

*289, 291. 
Reproduction in flowering plants, 

212-215*. 
Reproduction in fungi, *258, *259, 

*260, *261, *262, *265, *266, 

*268, *270. 
Reproduction in morning-glory, 

390, 391. 
Reproduction in mosses, *284, 285. 
Resin passage, *93. 
Respiration, 172, 173. 
Retuse, *131. 
Rhachis, 287, *288. 
Rhizoids, hairs serving as roots in 

mosses and liverworts, *282, 

*289. 
Rhizopus, study of, 257, 258, 259. 
Rhodophycese, 232. 
Rhubarb roots, *47. 
Ring, annual, *100, *101. 



Ringent, *203. 

Rise of water in stems, 108-113. 

Rockweed, study of, 250-252*. 

Root, 36-61. 

Root, adaptation to work, 59, 60. 

Root-cap, *42. 

Root-climbers, *39, 73. 

Root, dicotyledonous, section, *44. 

Root, elongation of, 30, 31. 

Root, exogenous, *44. 

Root, fleshy, 45, 46, *47. 

Root-hair, 31, *32, *49, 50. 

Root-pressure, 54, *55. 

Root-section, *42, *44. 

Root-sheath or root-pocket, 37. 

Root-system, 47, 48. 

Roots, absorbing surface of, 49, 

50. 
Roots, absorption and temperature, 

55, 56. 
Roots, adventitious, 36. 
Roots, aerial, 36, *37, *38, *39. 
Roots, brace-, *38. 
Roots, fascicled, *41. 
Roots, fibrous, *41. 
Roots, growth of, 30, 31. 
Roots, hemlock, lateral extension 

of, *60. 
Roots, movements of young, 56, 

*57, *58, 59. 
Roots, parasitic, 39, *40. 
Roots, primary, 36. 
Roots, propagation by, 61. 
Roots, selective action of, 54. 
Roots, soil-, 36. 
Roots, storage of nourishment in, 

46, *47. 
Roots, structure of, 41-46. 
Roots, water, 37. 
Rootstock, 75, *76, *77. 
Rotation of protoplasm, *184, 185. 



INDEX 



409 



Eound-leafed mallow, stamens and 

pistils of, 364. 
Eussian thistle, *379. 
Russian thistle, spread of, 394. 
Rust, 259. 

Rust, wheat, study of, 259-262*. 
Rye grass, 76. 

Sage, pollination in flowers of, 

*365, *366. 
Sago-palm, 113. 
Salver-shaped, *202. 
Salvinia, *302. 
Sap, descent of, *109, 110. 
Sap, rise of, 107, 108, *109. 
Saprophytes, 169, 269. 
Sapwood, 105. 
Scalloped, *132. 
Schizomycetes, 232. 
Schizophycese, 232, *238. 
Scirpus, cross-section of stem of, 

*84. 
Sclerenchyma, 84. 
Scouring-rush, study of, 292-295*. 
Seasonal plants, 311. 
Secondary growth, *96, *97, *100. 
Secondary root, 36. 
Secondary roots, direction of, 59. 
Sections, leaf, *151, *154. 
Sections, root, *42, *44. 
Sections, wood, *100, *101, *102. 
Sedge, rootstock of, *76. 
Seed, 5-24. 
Seed-leaf, *6, 7. 
Seedlings, 25-35. 

Seedlings, mutilated growth of, 14. 
Seed-plants, 231, 233. 
Seed-plants, classes of, 233. 
Seeds, containing poisons, 24. 
Seeds, dispersal of, 377-386*. 
Selection, natural, 395. 



Selective absorption, 53, 54. 

Self-pollination, 353. j 

Sepal, 197. 

Separated flowers, 199, 200, *201. 

Sequoia, *66, 71, *106. 

Series, plants form a, 300. 

Serrate, *132. ' 

Sexual generation, 278. 

Shade plants, *321. 

Shoot, 30. 

Shrubs, 69, 70. 

Sieve-cells, *93, 110. 

Sieve-plate, *93, 

Sieve-tubes, *93. 

Silica, 165, 241, 294. j 

Simple leaves, 137. 

Simple pistil, 202. 

Simple umbel of cherry, *187. | 

Sinuate, *132. J 

Sleep of leaves, *144, *145. | 

Slime-fungi, 232. ; 

Slime moulds, 178, *179, 180, 181, "i 

*236, 237. j 

"Smilax," 79, *81. 
Snowflake, pollen tube of, with 

generative cells, *214. 
Solomon's seal, parallel-veined leaf j 

of, *136. : 

Soredia, 271. ! 

Sori, 261, 287, *288. | 

Spatulate, *131. ! 

Species, 229. ; 

Spermagones, 271. j 

Spermatia, 271. 
Spike, 188. 

Spine, *347, *348, *350. 
Spiral vessel, *92. ' 

Spirogyra, study of, 241, 242, *243, 

244. 
Sporangium, 287, *288. j 

Spore, 235, *236. j 



410 



FOUNDATIONS OF BOTANY 



Spore-capsules, 281. 

Spore-cases, *258, *259. 

Spore-fruits, *254. 

Spore-plants, 231, 232. 

Spore-plants, classes of, 232. 

Spore-sacs, 263, 270, 273. 

Spores of slime moulds, 180. 

Sporophyll, 294. 

Sporophyte, 281, *282, 284, 285, 
289, 291. 

Spruce, fertilized ovule of, *303. 

Squash seed, 5, 6. 

Squash seed, section, *6. 

Squash seedling, 25-27. 

Stamen, *197, 201, 202, *203. 

Stamen, parts of, *203. 

Standard, *199. 

Starch, 17-20, *19. 

Starch disappears during germi- 
nation, 21. 

Starch in leaves, 169, *170. 

Starch-making, rate of, 170, 171. 

Starch, testing seed for, 18. 

Stem, 30-117. 

Stem, definition of, 62. 

Stem, dicotyledonous, annual, 
gross structure of, 86, *87. 

Stem, dicotyledonous, minute 
structure of, 86-98*. 

Stem, early history of, *95, 96. 

Stem, functions of cells of, 105, 
106, 107. 

Stem, modifiability of, 79-82*. 

Stem, monocotyledonous, *83, *84, 
*85, 86. 

Stem, structure of, 83-103*. 

Stemless plants, *72, 73. 

Stems, 62-118. 

Stems, climbing, 74, *75. 

Stems, storage of food in, 113-115. 

Stems, twining, *75. 



Stem-structure, early history of, 
*95, 96. 

Sterigmata, *266. 

Sterilization, 238. 

Stigma, 201, *203. 

Stigma, structure of, 213-215* 

Stinging hair, *184. 

Stipa, cross-section of rolled and 
unrolled leaves of, *318. 

Stipe, *264, 265. 

Stipules, *135, 136. 

Stolon, with tips rooting, *374. 

Stomata, 104,*151, *152,*153,*154. 

Stomata, operation of, 158, 159. 

Stone-fruit, 224. 

Storage of food in the root, 46, *47. 

Storage of food in the stem, 113- 
117. 

Strawberry, *226. 

Struggle for existence, 387-394. 

Study of buttercup flower, 195, 196. 

Study of lemon, 217, 218. 

Study of tomato, 217. 

Study of trillium flower, 192, 193. 

Study of tulip flower, 194, 195. 

Style, 201, *203. 

Sugar, 13, 116, 117, 168, 171, 172. 

Sugar, formed during germination, 
13. 

Sugar-cane, cross-section of a bun- 
dle from, *110. 

Sundew, *341, *342, 343. 

Sun-plants, *321. 

Supernumerary buds, 122, *123, 
*124. 

Survival of the fittest, 394, 395. 

Swarmspores, 180. 

Sweet pea, flowers, *199. 

Symbiont, 340. 

Symbiosis, 273, 340. 

Symmetrical, 198. 



INDEX 



411 



Taper-pointed, *131. 

Taproot, *41. 

Teleutospores, *262. . 

Temperature and root-absorption, 
55, 56. 

Temperature, relation to germina- 
tion, 9. 

Tendril, *138. 

Tesndril climbers, *74. 

Terminal bud, 63, 121, 122, *124, 
*125. 

Terminal flowers, 186, *191. 

Tertiary root, 36. 

Testa, 6. 

Tetraspores, *255. 

Thallophytes, 232, 235-275. 

Thallophytes, study of, 237-273*. 

Thallus, 235, 250. 

Thermostat, 9. 

Thistle, Eussian, *379, 394. 

Thorns as branches, 68, *69. 

Thyme, stoma of, *153. 

Tickle-grass, *381. 

" Timber line," *329, *330. 

Tissue, 94, 95. 

Tomato, study of, 217. 

Tracheids, 92, 93, *94. 

Transition from stamens to petals, 
*209. 

Transpiration, 156, 

Transpiration, amount of, 164, 165. 

Transpiration, measurement of, 
159, *160, 161. 

Transportation by water, 380, 381. 

Trees, 69. 

Trees, age of, 71. 

Trillium, study of flower of, 192, 
193. 

Trimorphous flowers, 367. 

Tropseolum leaf , *132. 

Tropseolum leaves, starch in, *170. 



Tropseolum, petiole, coiling of,* 75. \ 

Tropical vegetation, 324, 325. 

Tropophytes, 311, 318, 319. 

Truncate, *131. 

Trunk, *e6, *67. 

Tuber, 76, *78. j 

Tubercles on clover roots, *339. ^ 

Tubular corolla, *203. 

Tulip, study of flower of, 194, 195. \ 

Tumble-weeds, 378, *379, *380. \ 

Turgescence, 184. 

Turnip, seedling, *32, 

Twayi3lade, beetle on flower of, ! 

*359. \ 

Twigs, study of, 62-64. | 

Twiners, 74, *75. I 

Twining, rate of, 74, 75. i 

Types, order of appearance of, | 

298-305. i 

Umbel, *187. i 

Umbellet, 190. j 
Underground stems, 75, *76, *77, j 

■ *78, *79. i 

Uneatable plants, 348. ; 

Union of pistils, 202, 203. \ 

Union of stamens, 201, 202. i 

Uredospores, 261, *262. ' 

Usnia, *271. ' 

I 

Vacuole, contractile, 180. : 

Variety, 229, 230. i 

Vaucheria, study of, 245, *246, I 

247. 
Vegetable physiology, 1. 
Vegetation, alpine, 328, *329, *330, 

*331. 
Vegetation, aquatic, 332, 333. 
Vegetation, arctic, 327, *328. 
Vegetation, regions of, 324. ; 

Vegetation, temperate, 325, 326. 



412 



FOUNDATIONS OF BOTANY 



Vegetation, tropical, 324, 325. 
Vegetative organs, 30. 
Vein, 130, *133, *136. 
Veining, *133, *136. 
Venation, *133, 134, 135, *136. 
Venas flytrap, *343, 344. 
Vernation, 125, *126, 127. 
Vertically placed leaves, 146, *147, 

148. 
Vessel, *92, 106. 
Volva, *265. 

Water, absorption by roots, 53-55. 
Water, amount transpired, 159- 

165. 
Water, course through leaf, 163, 

164. 
Water, excretion of, 172, 173. 
Water, movement of, 107, *108, 

*109, *110, 111, 112, 113. 
Water, relation to germination, 10. 
Water-lily, white, insertion of 

floral organs, *205. 
Water-lily, white, transitions from 

petals to stamens in, *209. 
Water roots, 37. 
Weapons of plants, 349-351*. 
Wedge-shaped, *131. 
Weeds, 387-390. 
Weeds, study of, 388, 389. 
Wheat-grain, section of, *19. 



Wheat rust, study of, 259-262* 

Wheel-shaped, *202. 

Whorled, *293, 294. 

Willow, adventitious buds of, 128. 

Willow, arctic, *328. 

Willow, flowers of, *201. 

Wilting, 111. 

Wind-pollination, 354. 

Windsor bean sprouting over mer- 
cury, 56, *57. 

Winged fruits, 377, *378. 

Wings, *199. 

Wood, coniferous, structure of, 92, 
*93, *94. 

Wood of linden, *100. 

Wood sections, *100, *101, *102. 

Wood, structure of, *93, *100, 
*101. 

Wood-cell, *89, *91, *101. 

Wood-parenchyma, 94. 

Xanthoria, *271. 
Xerophytes, 311, 313-317* 

Yarrow, head of, *189. 
Yeast, study of, 266-270, *268. 
Yucca, 335. 

Zones, vegetation of, 324-328. 
Zoospores, 236, *244. 
Zygospores, 236, *243, *259. 



lyu*^ 



